I haven't seen it on 7.6.400, mainly because I haven't seen Progression since 7.6.300...but I've seen the issue happen during upgrades. It had multiple causes, and I'll present the two I've experienced.
1. Update scripts hose syspass and/or syscomp tables. With one client, they restored back to the previous version and we manually applied the DTS pacakages to their install, skipping the one that updated the security tables. In another case, the user needed to have some of the updates made to security, so they manually corrected the problem.
2. The update process did not update or incorrectly updated the dll that reads the syspass and syscomp tables (the name escapes me). The syspass and syscomp tables were perfectly fine, but the dll that reads the tables was doing so improperly. The correct dll was put in place and everything worked fine. This was also an issue back in 7.6.100 when PWE.exe was declaring a client side versus a server side cursor, but that was corrected, and I highly doubt an issue that old has resurfaced, just because of the change in compilers between 7.6.100 and 7.6.200
