If you have tried various balances without luck have you considered the remaining train wheels, mainspring barrel etc ?
If the train is free running then that eliminates one thing, if under mainspring tension the pallets move with gentle push of peg wood then this eliminates pallet staff or other issue. Always start from one end and work to the other eliminating each until all is working correctly, like so >
Mainspring > Drive Train > Pallets > Balance
If there is a fault with the preceding parts of the movement then no balance you use will work.
If the issue is with the balance wheel area then you must eliminate all the possibilities that remain, such as >
Jewels
1) Are jewels clean and undamaged - No pivot wear/debris/dry oils etc
2) Are the jewel seats/fixed jewels damaged or blocked ?
3) Are jewel blocks at correct Height or have then been knocked out of position ? ( if applicable )
4) Are shock Springs correctly installed and correct orientation ?
Balance Wheel
1) Is hairspring flat and concentric ? Is there kink or sticking of springs/magnetism ?
2) Is the staff true, or bent pivot ?
3) Dry oil stuck to pivot tips ?
4) Is the rim true or bent ( you can check this by removing hairspring and placing back in mainplate with cock )
5) Is the roller damaged/fitted correctly ?
6) Is the balance cock jewels correctly fitted or are they out of position ?
7) Is the roller table catching the lower shock area preventing motion ?
8) Is balance hack ( if applicable ) correctly positioned or blocking ?
Cock/Bridge
1) Is the cock/Balance bridge true or is it bent ? ( fitting the balance to main plate if no motion, raise cock with tweezer gently, if motion presents itself, then cock may be untrue )
I don't want to come across as telling you how to suck eggs but i face similar issues week in week out and i have to go Sherlock Holmes on the movements i service ( elimination ) and finding the answer is always a case of elimination. There is always a cause or causes, you just have to find which one or many there are until you can solve it.
MrBeat
* As a side note ive often found with seikos that dont want to chooch the pallets/escape wheels are defective