I'm kind of curious what browser and OS version you and the other user are running.
I'm running Firefox Nightly, which is version 66 at this point with tree style tabs 2.7.9 on auto update on linux 4.19 with intel/nvidia gpu drivers. I've never seen any issues just tree style tabs but note I only have 5 extensions at this point.
I was wondering if it was an issue with a particular platform or interaction between multiple extensions particularly if you are using the pre quantum version.
I'm running Firefox Nightly, which is version 66 at this point with tree style tabs 2.7.9 on auto update on linux 4.19 with intel/nvidia gpu drivers. I've never seen any issues just tree style tabs but note I only have 5 extensions at this point.
I was wondering if it was an issue with a particular platform or interaction between multiple extensions particularly if you are using the pre quantum version.