Am not aware that 3.x specifically addressed the issue ... for that matter not sure there ever was an official tracker bug reported with directions on how to reproduce the error. One would have to have a sandbox clone of a production site that had the issues and purposely wreck/disable/putz to get consistent behavior, me thinks. This to say, don't think I've ever been able to say .... xyz is cause in every case.
To many variables involved ... recently investigated a shared hosting environment where op had option to increase package restrictions that appeared to be the culprit ... cap on how much extra memory could be called by a Moodle script. A standalone or even a virtual where op had full control that wouldn't have been an issue .. or the 'fix' could have been applied.
Fingers crossed that and upgrade wouldn't make it worse! ;)
'spirit of sharing', Ken