A PES file that uploads fine on one shop's tool and rejects on another is almost always one of six things. Work through them in order — the cheap checks first.
1. Wrong file extension on a non-PES
Sometimes a customer sends a .pes file that's actually a renamed DST or PNG. Open the file with a hex viewer or just check the first four bytes — a valid PES file starts with #PES followed by the version code (e.g., #PES0100, #PES0050). If the header doesn't start with #PES, the file isn't a PES regardless of extension. Re-export it from the source tool in the actual format.
2. Truncated download
PES files transferred over flaky Wi-Fi sometimes truncate. The header parses fine but the stitch records cut off mid-design. ValidStitch flags this as 'incomplete stitch records'. Re-download the file from the original source on a wired connection.
3. Version-10 file on a tool that only reads to v6
Modern PE-Design exports as PES v10. Some older shop tools cap at PES v6 and refuse anything newer. ValidStitch reads v1 through v10, but if you got the file from a partner shop that exported on a very-old PE-Design release, the version mismatch can cause weird parsing failures. Ask the partner to re-export at the lowest version their tool supports.
4. Stitch count above 500,000 in an older PES variant
Older PES versions cap stitch count near 500k. Designs above that ceiling silently truncate on export from older PE-Design installs. ValidStitch flags this as 'design extent does not match stitch records'. Re-export at PES v10 or split the design into two passes.
5. Embedded thumbnail mismatch
PES files carry an embedded thumbnail rendered at export time. If the file was edited outside PE-Design (e.g., in Embird) without re-rendering the thumbnail, the thumbnail can be a stale image while the stitch data is current. This typically does not block upload but does cause a 'thumbnail does not match design' warning. Re-export from a tool that regenerates the thumbnail.
6. Encryption / password protection
Some commercial PES designs ship password-protected, especially from licensed-character vendors. ValidStitch cannot validate an encrypted PES — there's no key to decrypt the stitch records. You'll need to request an unencrypted version from the licensor.
If none of the six resolve the upload, attach the file plus the upload error message to support — we can reproduce server-side and tell you which parser branch failed.