This behavior starts after BBT calls Zotero.ItemTreeManager.refreshColumns(). If I don't do that, the problem does not appear.

I've been experiencing the same issue (see discussion here https://github.com/Dominic-DallOsto/zotero-reading-list/issues/27) and think I have found the cause of the issue and a workaround.

Basically, every time `Zotero.ItemTreeManager.refreshColumns()` is called, a CSS rule is added to the stylesheet for each custom column, setting the `flex-basis` to some value. If `refreshColumns` is called again (when re-adding the custom column or having a different plugin that adds a custom column) then a second instance of this CSS rule is added that somehow conflicts with the first and sets a different `flex-basis` value which causes this buggy column resizing behaviour.

If you select the custom column header HTML element in the browser debug tools and disable all but the first CSS `flex-basis` rule - everything works again.

I created a workaround for my plugins here (https://github.com/Dominic-DallOsto/zotero-reading-list/blob/master/src/utils/itemTreeStyleSheetBug.ts) that patches the stylesheet's `insertRule` function (that is called after `refreshColumns`) to ignore the adding of these conflicting CSS rules.

I guess a proper solution would require editing Zotero custom column API to not add these duplicate CSS rules.

If this happens for you with custom columns added by Zotero plugins, I think the issue described here (https://groups.google.com/g/zotero-dev/c/aM3I-8etB0c) could be responsible, and should hopefully be fixed soon.

If it still happens without any plugins / custom columns added - then it's probably a different issue.

this add on will also create the issue https://github.com/scitedotai/scite-zotero-plugin

1306266725

1. Activating scite-zotero-plugin
2. Adding a column of the plugin
3. Resizing the column will result in the same "glitchy" behavior, as it tries to expand the bar, especially if the column name is long