Outdated Serum colorization cache
What it means
This ROM's Serum colorization cache is in an old format that libserum 2.5.0 and later reject.
Why it happens
libserum 2.5.0 (DMD Extensions 2.4 and later) rejects a .cROMc cache of format below 5 and regenerates it if the .cRZ or .cROM source file is in the same folder. Pincab Toolbox can set the old cache aside without deleting it. If the loaded libserum version is unknown, this finding is only a note.
How Pincab Toolbox detects it
The .cROMc file in the ROM's altcolor folder starts with CROM and its format number (2 bytes) is below 5. The scan moved nothing.
Automatic repair
Repair, included in the Pincab Toolbox licence, can fix this one for you. Your files are backed up first, and the fix can be undone. €3.99, one purchase. Run the free scan first: it confirms this is really your case.
Check your own pincab
Pincab Toolbox is a free Windows scanner for Visual Pinball X and PinUP Popper. It finds and explains problems like this one. No account, no telemetry.
Download for freeCovered: Visual Pinball X (10.x) and PinUP Popper. Partly covered, read only: PinballX and PinballY (their settings and game lists). Not covered: Future Pinball, Pinball FX, Visual Pinball 9 and the other frontends.