Prusa Connect Rejects bgcode When Filament Color Uses Specific RGB Values

[jw24425]

Description of the bug

Prusa Connect fails to accept bgcode files generated from a specific .3mf project when the filament color for Extruder 1 is set to certain RGB values (notably 0/255/255, 0/254/255, 0/255/254). The same bgcode uploads correctly to the printer’s local storage, loads in the Prusa G‑code Viewer, and prints normally. Changing the filament color by even 1 point resolves the issue - e.g. 0/254/254 or 1/255/255.

This appears to be a metadata parsing bug in Prusa Connect, likely triggered by specific RGB values in the bgcode header.

Project file & How to reproduce

Project file.zip

Steps to Reproduce

1. Open the attached .3mf project.
2. Slice using the included printer and filament profiles.
3. Ensure Extruder 1 filament color is set to one of the following RGB values:
   • 0 / 255 / 255
   • 0 / 254 / 255
   • 0 / 255 / 254
4. Export bgcode.
5. Send G-Code to printer host

Observed Behavior

• Upload initially appears successful, but the file does not appear in the Prusa Connect file list.
• After refreshing, Connect briefly displays: “Files Can’t Be Uploaded.”
• The file does appear under the printer’s local storage (Physical Printer → Local Files).
• The bgcode loads correctly in the Prusa G‑code Viewer.
• In one instance, the file eventually appeared in Connect (after slicing variations), with the thumbnail appearing a generic placeholder, not a rendered preview.
• Changing the filament color by 1 RGB point (e.g., 1/255/255 or 0/254/254) makes the upload work normally.
• Changing geometry or adding elements also avoids the issue, but changing infill does not.

Checklist of files included above

• Project file
• Screenshot

Version of PrusaSlicer

v2.9.4

Operating system

Windows 11

Printer model

Prusa mk4s