Hi, My 380 (tiptronic) in manual once it reaches temp on warmer days is often intermittant for gear selection up or down. It will also often drop straight into Drive, with selector in manual and selecting a higher gear. Works correctly at cool temps. Had it fixed under warranty a couple of years ago, it was apparantly a simple fix!! Any advice would be greatly appreciated.

your box is displaying normal behaviour as it limiting damage due to heat. Try getting a tranny cooler fitted to extend the boxes life

Mine has done this since purchase when towing. Agree it is a sensor telling the computer tranny is overheating so does its own thing even in manual mode.
New trans computer, new valve body, transmission cooler, check of micro switches, reset of computer multiple times and two fluid flushes with genuine Mitsubishi fluid with no improvement.
One tube of mr tranny additive purchased off eBay corrected this and a long term shudder problem.

Interestingly about 12 months ago was speaking to a guy with a new challenger who was experiencing exactly the same problems with his five speed auto when towing.

Thanks for the feedback. I fitted a large cooler a couple of years ago. Flush and new oil c/o about 30k ago! Oil looks OK, translucent Red. Will do an oil chg anyway. The last time this happened 2-3 years ogo, the dealer (still under warranty) fixed the problem, but I can't remember the fix! Will also look ant mr tranny! Cheers.