After upgrade from 54.0.1 to 55 it became impossible to reorder tabs using drag-and-drop - after moving tab it jumps back. I've found this report https://bugzilla.mozilla.org/show_bug.cgi?id=1367136 and can confirm: after changing toolkit.cosmeticAnimations.enabled to false (default is true) this issue is fixed (except I've no idea what exactly toolkit.cosmeticAnimations.enabled does and what else has changed because of this workaround).
I am unable to duplicate this bug, can you test with a clean profile and see if you can still produce it please.
I'm sorry, but I've downgraded to FF 52 ESR because of coming FF 57 which will kill many must-have (to me) plugins - no reason to debug FF 55 and then try FF 56 just to switch back to 52 when 57 will be released. Feel free to close this issue if no one else is affected.
Please feel free to reopen and update any bug report that can be duplicated with current esr builds, 60.x. If you feel your feature needs to be re looked at in any of these bugs reopen and update, please attach patches when appropriate. Thank you Mozilla Team
