There’s quite a few interesting passages in the 1861-63 Manuscripts outlining how crisis is endemic to the specifically capitalist form of social labour. One of the reasons is neatly outlined in the following:
The possibility of crisis, which became apparent in the simple metamorphosis of the commodity, is once more demonstrated, and further developed, by the disjunction between the process of production (direct) and the process of circulation.†a As soon as these processes do not merge smoothly into one another [XIII-713] but become independent of one another, the crisis is there.
And given more detail in the passages that follow:
The possibility of crisis is indicated in the metamorphosis of the commodity like this:
Firstly, the commodity which actually exists as use value, and nominally, in its
price, as exchange value, must be transformed into money. C — M. If this difficulty, the sale, is solved then the purchase, M — C, presents no difficulty, since money is directly exchangeable for everything else. The use value of the commodity, the usefulness of the labour contained in it, must be assumed from the start, otherwise it is no commodity at all. It is further assumed that the individual value of the commodity=its social value, that is to say, that the labour time materialised in it=the socially necessary labour time for the production of this commodity. The possibility of a crisis, in so far as it shows itself in the simple form of metamorphosis, thus only arises from the fact that the differences in form — the phases — which it passes through in the course of its progress, are in the first place necessarily complimentary and secondly, despite this intrinsic and necessary correlation, they are distinct parts and forms of the process, independent of each other, diverging in time and space, separable and separated from each other. The possibility of crisis therefore lies solely in the separation of sale from purchase. It is thus only in the form of commodity that the commodity has to pass through this difficulty here. As soon as it assumes the form of money it has got over this difficulty. Subsequently however this too resolves into the separation of sale and purchase. If the commodity could not be withdrawn from circulation in the form of money or its retransformation into commodity could not be postponed — as with direct barter — if purchase and sale coincided, then the possibility of crisis would, under the assumptions made, disappear. For it is assumed that the commodity represents use value for other owners of commodities. In the form of direct barter, the commodity is not exchangeable only if it has no use value or when there are no other use values on the other side which can be exchanged for it; therefore, only under these two conditions: either if one side has produced useless things or if the other side has nothing useful to exchange as an equivalent for the first use value. In both cases, however, no exchange whatsoever would take place. But in so far as exchange did take place, its phases would not be separated. The buyer would be seller and the seller buyer. The critical stage, which arises from the form of the exchange — in so far as it is circulation — would therefore cease to exist, and if we say that the simple form of metamorphosis comprises the possibility of crisis, we only say that in this form itself lies the possibility of the rupture and separation of essentially complimentary phases. But this applies also to the content. In direct barter, the bulk of production is intended by the producer to satisfy his own needs, or, where the division of labour is more developed, to satisfy the needs of his fellow producers, needs that are known to him. What is exchanged as a commodity is the surplus and it is unimportant whether this surplus is exchanged or not. In commodity production the conversion of the product into money, the sale, is a conditio sine qua [non]. Direct production for personal needs does not take place. Crisis results from the impossibility to sell. The difficulty of transforming the commodity — the particular product of individual labour — into its opposite, money, i.e. abstract general social labour, lies in the fact that money is not the particular product of individual labour, and that the person who has effected a sale, who therefore has commodities in the form of money, is not compelled to buy again at once, to transform the money again into a particular product of individual labour. In barter this contradiction does not exist: no one can be a seller without being a buyer or a buyer without being a seller. The difficulty of the seller — on the assumption that his commodity has use value — only stems from the ease with which the buyer can defer the retransformation of money into commodity. The difficulty of converting the commodity into money, of selling it, only arises from the fact that the commodity must be turned into money but the money need not be immediately turned into commodity, and therefore sale and purchase can be separated. We have said that this form contains the possibility of crisis, that is to say, the possibility that elements which are correlated, which are inseparable, are separated and consequently are forcibly reunited, their coherence is violently asserted against their mutual independence. [XIII-714] Crisis is nothing but the forcible assertion of the unity of phases of the production process which have become independent of each other. MECW 32 139-40