I have discussed this briefly in a previous post but nothing was ever resolved.
I have had an A16 Ultra now for about 2 and a half years during which it was treated extremely well. After moving house a couple of months ago I hooked the unit up and turned it on. I noticed after a couple of mintues that the Master Sync LED had not turned from orange to green.
After going through all my connections and swapping cables everywhere I unhooked everything but the power supply and tried booting the unit in Master Sync mode (I usually use it in Z-Link Sync mode). The unit still wouldn't boot. Instead of the usual 'sizzling' sound of the input LED's flashing on momentarily the Master Sync LED just stayed orange. The Samplerate light did turn on and the sample rate could be changed, but the A16 Ultra would not respond to input or output of either analog or digital audio. No metering and no sound. ADAT outputs would not light up either.
I confirmed that the PSU was not the problem and after getting no useful information from SonicCore I took the unit to a repair centre locally. Coincidentally at the time I put mine in for repair someone else had dropped their A16 Ultra to the same repair centre with similar problems as well as one extra, which was that the Master Sync LED wouldn't light up at all.
The repair centre handed the unit back to me having had it running for a day or so in Master mode with 'no problems'. I subsequently took it home and plugged it all back together. It stayed working for about half an hour. ( $115 repair for half an hour operation....not too cost effective)

After taking my A16 Ultra back to the repair centre and leaving it there for a couple of weeks I was told that neither my unit or the other that was left there could be repaired.
Having hooked up my brand new MOTU 2408 MkIII a couple of weeks ago and enjoying using that, I thought I'd give myself a chuckle and turned on my A16 Ultra. This time it booted.

After a few hunches and some futher testing I have figured out that trying to boot the unit with any kind of external Sync input affects its boot up, but Z-Link is the worst. After connecting with Z-link the unit may not boot for days.
Now....this to me says faulty capacitor somewhere in the sync input path - if there is such a thing - but the repair centre told me they had replaced a number of suspect capacitors as a precaution so if there was such a faulty cap then I would have thought it was replaced.
I have noticed at least one other user on the forum that has had a similar problem, but I'm wondering if anyone has had a solution? Has anybody had this problem and actually had it rectified by either a local repair centre or by Creamware/SonicCore?
Thanks,
AudioDan