I'll be doing a bit of testing myself; your idea has merit.
(I'll be trying Cleanlook instead of FIVE to see if things get worse for me.
PB themes *aren't* just reskins so they *could* be a vector for bugs. (Its the price of flexibility.) I could live with the odd Theme-induced annoyance *if* I knew it was in fact Theme induced and it was my choice.
Presumably the Guys in Kiev should be looking into this possibility since they seem to be pulling their hair off trying to figure out why 15.2 seems less stable on PB360 than on 301. It *might* exonerate the firmmware itself or at least point them in the right direction if they're still unsure what is going on. And, well, the theme builder still targets the 301 primarily so there could be issues...
It's an interesting idea, worth looking into.