Your CD which failled will be a Mode1 format CD. This causes the Mk3 to crash. Make sure you burn as a Mode2/Form1 format and then the Mk3 will load the SW OK. Check the disc is error free before you use it (surface scan, quality check)

Last valid SW version for the Mk3 is 3-1/63, which is on every OS disc from v22 onwards.

If you used OS disc v21.1 then the nav will have 3-1/62 loaded.