Took my little boat out to a local pond last weekend…first trip…and the TM sonar/transducer temperature just ‘free-fell’…water temps started at 50°F and then it just scrolled down to eventually settle at 4.5°F (really, not a scientific possibility)…
Talked to Ronnie over at Lowrance about it…he walked me through a ‘soft re-set’…which resets the software/hardware (pretty non-technical here 
)…and fixed the problem.
At any rate, I’m thinking this might become a ‘spring ritual’ (like tightening up the brake on my baitcaster before the first cast 
)…
To do a soft re-set, start with the Lowrance unit ‘off’…press/hold the ‘pages’ button then press the power button…
Key is, if you have wayppoints saved to the unit, you’ll want to back them up on an MMC or SD card first otherwise they’re ‘wiped’ and you lose them.
Thought I’d share.