The earlier 12 pin TSM's don't seem to be quite so fragile as the later 18 pin items.....but they do still fail. The 12 pin ones are only available via Morgan. If you have problems with rear lights, it's worth checking the cable loom under the leather strap at the boot lid hinge as well, it does get crushed and the wires break and short out there, certainly worth protecting better if they are OK still.
I agree with all the other comments about the fuel pump being the problem with your M3W. I did the first Walbro pump fit and it is still going strong with no issues. It's well worth replacing the standard pump even if you have no problems. It will fail at some point and probably at the most inconvenient time, much better to do it in the garage with all the tools and parts available.
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