Help with Pfaff 346-H3 skipping stitches and rotating bobbin case

[Lucasn7]

16 hours ago, mikesc said:

Check your thread path further up..in particular the "take up spring" ( check spring ) ..it may be keeping the thread too taut..that will make it "snap".. and make the bobbin and hook click and miss occasional stitches..as can the timing being very slightly retarded.

I threaded the machine according to the official user manual so that should not be causing any problems. 
The take up spring might be to taut because it is made (and adjusted) to be pulled by two threads at the same time for both needles. I've adjusted the spring and i'll keep experimenting. 

[Lucasn7]

15 hours ago, Wizcrafts said:

You can move each hook drive laterally. There should be frames holding the hooks that can be moved by loosening big screws. There will also be a bendable deflector on each bobbin case that is supposed to push the needle ever so slightly out of harms way as the tip of the hook approaches it. If your hook tips have burrs, they need to come out and be buffed smooth again, or replaced.

Indeed i've noticed the tracks and slots but never knew they were for moving the hook drives. When i look closely i can see that the left bobbin assembly (scraping one) is a bit closer to the feed dog than te right one (second image). I've unscrewed the big screws in the slots and also on a block on the bottom side that looks like it needs to be moved in order to make room. But still i cannot move the hook drive. Also i'm a bit afraid to mess up the timing when adjusting the driving gear by loosen and fasten it... Any thoughts?   
Regards!

[Wizcrafts]

If you can't, or won't move the left hook assembly, try prying our the deflector tab a little to push the needle away from the hook. Most lockstitch machines pull the thread and needle to the left as they sew, which explains why that needle makes more contact than its right counterpart. I would personally try to move the left hook a smidgen. The timing gear can be tweaked later.

[Lucasn7]

Hi it's been some time since i replied to this thread because i was busy and after that i've only used the right needle. At this moment i'm making a bag and need to use the left needle again because the workpiece can't fit onder the arm properly.. If i use the left needle the thread or needle breaks in a few stitches. 

On 9/12/2019 at 5:54 PM, Wizcrafts said:

, try prying our the deflector tab a little to push the needle away from the hook

How does this work? I cannot figure it out. Also the machine looks like the whole hook assembly can be moved? Forward thanks