Custom fields get expanded even though cookie says not to

I was able to figure out that collapseTwixiBlocksFromCookie runs twice if the block exists as value in the cookie and therefore toggles the block twice. First it collapses the custom field's block which is right but then expands it again which is not the desired result. This can only be observed if a breakpoint is set for the appropriate function, otherwise it just looks like it never remembers the setting at all.

I checked all versions from 4.4.2 until 4.4.5 and the problem occurs in every version. Jira 5.0.2 does not contain the bug.

I have been searching for an existing bug like crazy but was unable to find one.

As reference: We are using a custom field to store stack traces, therefore it is quite obvious/annoying to us that it always expands the block.