Since I got the car back from the HG and chains job in February, I've had a random, elusive bong coming up a handful of times. First was just 10 days after the HG job, early March. Next time was last month on a drive home from work, when I got it twice within 10 minutes. I was unable to read the message on every occasion as it was very briefly displayed; I think there was just a bong and no message on one occasion.
This afternoon on my way back from work, I managed to catch the first few letters, definitely "TRANSFER..." and... (I assume)... BOX NEUTRAL
Pulled over after a few km, tried switching to low range and nothing would happen. Switching off and restarting the car seems to have brought things back to normal though. So tried a few cycles between high and low and it's all good.
No error messages and no error codes registered (I do get the "noise on actuator signal" but this has seemingly been for ever). Fuse 37 is not installed. Should I just forget about it or is there anything else I should be looking into?
Thanks in advance.

It's a common fault with the Transfer Box, caused by the electronic rotary potential sensor becoming worn over time.
There's a few threads on this issue so if you do a search you will come up with plenty of information. It's to do with the rotary potentiometer becoming worn over time. Unfortunately you can't just replace the item but have to either find a second hand one (they're like rocking horse poo!) or replace the whole transfer box electrics.
Had the same intermittent problem on my old MY05 TD6, but never able to get it sorted satisfactorily.

Thanks for the response. I've read each and every thread I could find on the matter. I was wondering if there are certain steps or escalation recommend before going for a new transfer case motor assembly. A calibration for example. Or simply try using the thing more often (I do change into low every couple months or whenever I remember).

A calibration won't help. Sometimes the problem is a cracked solder joint within the potentiometer assembly. If you're willing and able to remove the potentiometer, carefully prise it open, reflow the solder joints and seal it back up again, then you might be in luck. You've probably already seen pictures of the insides of the assembly in other threads.

Just did a calibration this afternoon. I do keep my expectations low, however. I'll watch it over the weekend and discuss with my garage on Monday. I've found a replacement motor assembly on eBay so I'll weigh my options once I've got a garage quote.
I'm handy enough to attempt taking the thing apart myself but I'm currently suffering from vertigo and even if I was well, I'm still useless with a soldering gun so the potentiometer would be out of my league...

Mine has done this since I bought it in April last year. Initially it would flash up and bong almost constantly. I took it to my local indy who checked and rerouted the wiring. This improved matters greatly but it did return after a few weeks (But not as often.) I sourced a reconditioned transfer box ECU and had that fitted. This has almost got rid of the problem, but not completely.
The car very occasionally flashes up "Transfer box neutral", "High Range" or "Transmission failsafe". None of these log codes or affect the car in any way so I have learned to live with them!

Interestingly, I had the "High Range" message once again, last Saturday. That's 2 months after the calibration. Cycled hi-lo-hi twice after next restart and it hasn't come back. I'm planning on changing the battery during next service as it will soon be on its 4th year and see if that helps, too. If this is a nuisance half a dozen times a year, I can definitely live with it and spend the money elsewhere on the car...