Bernette 90E The needle goes up and down but doesn't pick up the bobbin thread - I have checked that I have threaded correctly - cleaned out bobbin area for dust etc and changed needle - I haven't changed anythig - any idea what else to try?

Our Bernette E90 timing was off due to a jam (design flaw I think)...Instructions on how we fixed it.

1. To correct timing, tip over machine and unscrew inspection plate.

2. Find the gear and unscrew the 2 grub screws so the gear is free from the shaft

3. Turn the main sewing machine handle to manually get the hook (pointed piece) of the housing (see arrow) to be directly behind the needle

4. Hold it the tightly, and turn the handle again, the needle should be able to go up and down while holding the hook in position.

5. When the needle is at it lowest and starting to move back up and the hook is directly behind tip the machine over and tighten the 2 grub screws on the gear underneath.

6. Replace inspection cover and you’re done

Have a Bernette 90e and it is driving me mad! I could be sewing for weeks and then for no apparent reason, while sewing, the bobbin housing pulls right out of position and jams. I have, by luck only I must add, been able to put it back into the right position but it takes me days!. I do not no what to do and am about to chuck the whole machine. please help me!!