I also bought several components from Ti Parts Workshop.

Some where bad like the tensionner wheels with double bearings that indeed are a bad design (its a misunderstanding of the way of working the Brompton derailleur fork that require to work wheel that the whole wheel turns), some work well like the titanium-carbon rear rack.

For the bottom bracket, its reliable, I had no issue with moisture or water entering in it and my TPW bootom bracket is now about 8 years old.

The only issue is a well known one with titanium BB axle: titanium bolt are very difficult to be enough tightened in a titanium female thread, therefore that its better to use long stainless steel bolt.

Another issue that was encountered is that some Brompton had a badly threaded bottom bracket box, i.e. the threads of the two sides were not perfectly aligned what make he mounting of bottom brackets like the TPW with two separated bearings difficult. But this issue is not due to TPW and any bottom bracket with separated bearings will have problems.

About the asymmetry of the Brompton bottom bracket box, its 5mm to the left of the bike to have more room on the right side for the crankset and chainring, so the right axle is 5mm longer than the left axle to compensate and have symmetric pedals. With a symmetric bottom bracket, the pedals will be slightly asymmetric (which is not a major problem).