The PPC-R221 is considered end-of-life by Rexroth (Bosch Group). Official support is limited. If you experience a "Red WDG" or "Motherboard" fault, the only viable solution is to source a used unit from an industrial surplus vendor or migrate to the newer PPC-R22.2 series (which requires a full program conversion).
If the unit was recently replaced, ensure the firmware version on the CF card matches the hardware. Drive Diagnostics: rexroth ppc-r221 fault codes
When a fault occurs, the display typically flashes a code. Below are some of the most frequent errors encountered with this hardware: E200 Series: System Errors The PPC-R221 is considered end-of-life by Rexroth (Bosch