HP 82143A / HP 82162A foto coupler (encoder) - substitute

[AndiGer]

After some searching I finally ordered a Honeywell HOA1405 photo coupler.
For the printing picture itself it works well. All dots there, nice spacing. Printing numbers everything fine.
BUT: When I print alpha the printing is done completely but the print head stays in the left side. When I switch the printer off and on again the print head runs back to home position. Whatever I print after that (number or alpha) the printer performs a line feed before printing the next requested output.
If it is alpha again the print head behaves as described before. If it is a number the print head works as desired and comes back to home position.

Any idea solving that?