The drive has arrived yesterday, I ordered a TB1H from First-Supply to have it fast (they deliver from the UK).
The one I received is a HY-DIV268N-5A wich looks exactly the same.

I couldn't wait to have a look at the inside and removed the cover.
The board is floating inside, it has no screws holding it in place. The chip is fixed to the heatsink and the board is held in place horizontally by the cover screws wich go through the holes but these have some play. See picture.
The chip pins experience all the mechanical stress when the plugs are installed or removed.

Next I removed the chip to have a look a the bottom side of the PCB. There's no thermal paste or pad..... and the mounting holes have some burrs, the chip will not make good contact with the heatsink.
Deburred the holes and remounted with thermal paste for testing.

I use a 33V supply, 4Amp Sanyo Denki bipolar motor and did set the drive at 2.5A and 1/8 microstepping.
The drive works but the stepping rate seems wrong, checked the swicth settings again .... Short story: the microstepping table is wrong, looks like 2 colums need to be swapped.

To be continued...