Update: We swapped from running Sage 100 ERP Advanced 2013 as an APPLICATION to running it as a SERVICE. We were on a MS Server 2008 R2. We had to bump the memory parameter to 3072 (there are 40 concurrent users).
Details on the memory parameter change:
https://www.evernote.com/shard/s1/sh/4ba87667-d062-4c48-8046-c95a6cb27acb/b2f94b05fdc1253db9f036719422422f
After that the issue appeared to resolve (or at least it's not locking users periodically as it was when we ran this as an application).
Still unsure exactly what is/was going on here as we toyed with DEP regarding BEX issues.
And as described above - this was a customer on 4.5 who did just a single level upgrade. Makes me very skittish about large # of users under Sage 100 Advanced or Premium. The biggest concern is there is NO way to tell if you will have problems without putting Sage 100 ""under load' which means if you do have a problem you have a real problem. If you roll back to 4.5 you have to go do wksetup on 40 stations, if you toy with 2013 you potentially have 40 people in a wholesale distribution setting not taking orders, shipping, etc.
This is a pretty serious concern imho. Based on prior feedback that I've read here and elsewhere (Sage online) -- the problem seems to be the same whether you are on Advanced or Premium. IOW an upgrade to Premium does not automatically resolve this issue.