Firefox 58.x/59.0 with the WebGUI is switching back to Common partition randomly

I have noticed that when using the latest Mozilla Firefox versions (58.x and 59.0) with WebGUI from TMOS/BigIP version 12.1.3 then editing objects in partitions other than Common, the partition switches randomly back to Common in the WebGUI

This then causes errors when you try to save as the object is no longer referencing the correct partition (i.e. now Common)

As we have no issue with IE or Chrome that it is something new to Firefox but it has been driving me nuts. I have switched to using Chrome as a workaround.

Has anyone else had this effect or am I going mad ... I tried looking for other questions about this but found nothing related.