My Mini Pajero had exact same problem, I changed TCU twice, problem comes again.
I changed A/T gear twice, problem comes again in winter. So this winter, the trick was to warm it up for 10-15 minutes and then drive or you drive it as it is and after few KMs, turn the engine off and ten back on. The car starts working good.
I have also heard about this myth of heating up TCU and I also got heating plates to mount under the silver surface of the TCU but still could not get time to fix them.
Have you connected the peltier to het the TCU continuously or you have used some kind of timer ?