Question for the CONST glitch, which I just thought of: Does it still occur if the CONST name is all uppercase or lowercase? It may be an issue of the internal routines trying to compare UCASE$ names verses CaMeLcAsE stored names.
I finally got my PC in the shop for repairs today, so if I get it back next week, I'll dig into the issue better, but it may just be a simple case of cases not matching, which is causing the issue.