v2.2.3 has problems with "Animate tab" option. Ubuntu 18.04 LTS, Firefox 63.0 x64. When "Animate tab" animates - it causes some memory leaks or read/writes on HDD, so my PC will operate slower and slower and then it will completely frozen, and the only ways to avoid this - to click on monitored tab to stop favicon animationon, or to disable "Animate tab" option at all! Something became unstable with the last FF version.