Concurrent record locked happens when two processes try to generate the same Widget concurrently. One of them locks it, generates the data, releases the lock and then they both get the same cached data returned.
If you’re getting this error it usually means that something unexpected/fatal broke during that cache generation and the execution stopped before releasing the lock. It will release itself eventually, but you need to find and fix the root cause.
“Missing a temporary folder” is mapped through directly from PHP and probably means that your PHP configured temporary folder isn’t accessible.
In the mean time I’d encourage you to get the latest v3.3 as there are important security fixes between what you have and that release. 3.3.6 → 3.3.10 is a code patch only (no DB changes) which should make it easier to apply.