My speculation:

I guess the bug is a simple memory mis-procedure: When you switch items, the
memory buffer(?) which holds the previous item data must be freed, and
re-allocated for the new item data. But this procedure is not done, instead, we
try to add the new item data to the previous item data (causing a mess, and the
crash)
We only free the data when we drop the item, or unhover it. As switching items
is neither of those - we do not free the data, and jump straight to writing the
new item data (which doesn't crashes immediately, but corrupts all data,
crashing a little after, when processing the new autostr)