Mozilla when started for the first time brings "Convert Migration"
alert.  This is fine but it does that consistently the second time
too (although not the third).   Moreover once at such migration repeat,
when "Convert Profile" button was hit, it reacted with
'Segmentation violation (core dumped)' and dumped around 15 megabytes
of core.  It kept repeating that SIGSEGV until ~/.mozilla/ was deleted.
On subsequent tries I was unable to repeat that sequence.

Also every run ends up with a message on a screen:
"Runtime mismatch, so leaking context!".  No idea how related to
the above.