In arcade emulation, every ROM file must have a precise file size (length) and a specific checksum (hash) to be considered valid. If a file is even one byte off, MAME will flag it as having an "incorrect length". : avp.14m is a graphics (GFX) ROM.
Instead of hardcoding length, validate against an expected range or use a length field in the protocol: avp14m incorrect length
Some industrial HMIs or SCADA systems use structured text files (JSON, XML, or custom binary) to load parameters. The token avp14m could be a key expecting a fixed-length array. A mismatch between saved and schema-defined lengths triggers the error. In arcade emulation, every ROM file must have