It seems that, if you have the negative coin token & no money on hand but a lot of coin tokens & you click on something to buy, the UI doesn't take the -1$ into account, spends one less coin token than is needed, and leaves you unable to buy the thing you wanted.
This happened to me with dominate, but I assume it probably works with every card. Should be easy to reproduce. I didn't find this in the known bugs list, so I assume it's new.
Thanks for the report!
It's a new bug, similar to an older one with the -$1 token when debt was involved.