Import PTU spare part fails - suggestions needed!

Hi,

since my friends PTU (MD152999) failed with decreasing intervals (heat problem), we ordered a spare part from an US dealer (meanwhile we have 3 of these). MMC Germany could not supply it.

The spare PTU's do not work correctly: The RPM meter jumps in 500 rpm steps :( Our guess is that they all come from the same foreign source, as they do not have the imprints like the OEM PTU.

Did anyone of you experience the same problem? What did you do? Where would you buy a spare PTU?

Thank you,
Stefan