Print server needs to reboot when printing more than one time with Brother P750W

[JoLiSy]

Works excellent with Brother QL-1110NWB and QL-1110NWBc.
But with P750W it only prints two times before not accepting any further print requests.
The third print request is sometimes printed automatically when the print server is closed.

[JoLiSy]

After some more investigation:
The issue is related to network printing. E550W has the same issue when printing over network as P750W. Over USB everything works fine.
E550W also stops after two prints, just like P750W.

Sometimes a third print comes out after at least 1 minute, most often longer time.