Problems with editing transactions on Investing accounts

Normally I enter transactions like check writing before doing an auto-update, but this time I had a check which I accepted into an Investing account before entering it in the system. I then went to update the information, such as who it was written to, the category, and the memo. However, when I then hit Enter I got an error message about not being able to manually write the check number and it changed all of the information based on the last memorized transaction to that person. Even the amount had been changed! Luckily, I could edit everything directly to get it fixed, but this is a scary bug.

Anyone else see this and ideas on how to avoid it in the future?