TCodeToolManager.HandleException: [20170421200056]
Clearly a bug for the bugtracker.... (unless already there)
Lowercase filenames a correct, and good. Fpc and Codetools use certain variations to find files.
That is, on a case sensitive files system "WorkerUnit" would not be found, if it was saved as "workeRuniT.pas".
However "unit WorkerUnit" will lead to a search for: the given case, all lowercase, and IIRC all upper case.
As for more info on your issue:
1) Make sure every file that you use, is either:
- listed in the project inspector
- the "package window" of the package to which it belongs.
It should work without, if they are reachable (which I guess they are, or it would not compile).
But it may be worth a try. If it helps, mention it on the bug report.
2) Rather far fetched.....
Ideally you will not have added/edited anything in the "Path" section of the project options / package options.
That is not additional unit/include/ppu search pathes.
If you do have (and there are valid cases) make 100% sure that none of the path overlap. If a location on your disk is listed as a path in the project (or a package), then this location must under no circumstances be reachable through the path of any other package.
Note: if you did break above rule, you would likely have a ton of other issues. Nevertheless, I mention it, as I seen it countless times causing all sort of issues.