You know when you are cutting corners - well I do - and I was definitely cutting corners when aligning the track across the two boards. I knew what I should be doing but thought 'well, I know it is a bit fragile, so I will go carefully'. Some chance of that - inside two days the ends of the track on both boards were so mashed that running trains across was impossible and no amount of straightening would solve the problem.
This is an example:
I knew what I should have done, having been bitten by this before. Given that I am now retired, I have all the time in the world to do this properly, so why didn't I do that? The answer is to cut up some printed circuit board (pcb) into sleeper sized chunks, isolate the ends by cutting a channel through the copper, drilling a hole and fitting the board permanently to the baseboard. Then I solder the rails to the board and the rail ends won't go anywhere! I even went down to the local electronics shop and bought a clean sheet of pcb for the job. Why on earth didn't I do it? There is an old adage about tools - "buy cheap - buy twice". This should be amended to "take a short-cut - do twice!"
Anyway, I got down to the job the other night and this is what the board ends look like now.