Hello @RokeJulianLockhart,
After some further digging, it seems that the ACW-791 Molex Micro-Fit pinout differs from Teltonika’s 4-pin Molex PSU connector. On the ACW-791, the GND and V+ are located, let’s say, on pins 3 and 4, whereas our official PSUs use a different pin assignment. My guess is that this mismatch is the reason why your RUTXR1 does not boot when powered through the ACW-791.
For reference, here’s a related discussion on the Peplink forum that might be useful:
Best regards,