Since I recently dist-upgraded sid. Tried to: 1) run with empty profile 2) do apt-get dist-upgrade just now, restart - doesn't help
it seems to be freezing during rendering of the websites, seems like eventually running out of some resource and java-script heavy sites freeze it very soon. For example, if i open https://lichess.org/eTyPxe44EoQs (chess game analysis on lichess) first it opens fine, but hitting refresh certainly hungs whole firefox and only way to is kill it.
