This is the closest troubleshooting fault i can find that is similar to what you are saying:
Symptom:
When driving in sideward mode, the
machine 'locks up' when the wheels
have been steered in to a certain
position. Steering out frees the
machine.

Diagnosis
- Carousel Prox Malfunctioning
- DB horse Shoe set incorrectly
- DB valve Malfunctioning

Repair
- Check horseshoe for looseness
- Check Proximity Switch positioning
- Check PLC plug Connections
- Test Signal from PLC
- Check solenoid for 12V
- Check Solenoid Spool

hydraulic relief pressure settings:
Lift = 221bar (3205.33psi)
Reach = 107bar (1551.9psi)
Tilt Fwd = 107bar (1551.9psi)
Tilt Bkwd = 235bar (3408.39psi)
Auxillary = 107bar (1551.9psi)
Main Relief = 250bar (3625.94psi)


One other thing to consider is the main changeover valve may be malfunctioning but generally when the engine stalls when a hydraulic function is stalled that is a relief valve or diverter valve issue.

If you want to contact Combilift directly you can email the technical dept at [email address removed], (technical followed by @ followed by combilift followed by dot com)