Does anyone currently use Maxell 90m DATs and a TASCAM DA 30 mkII?
I haven't bought new DATS in a couple of years, but the last batch of Maxells I had were OK. I was using the green label tapes sold by the Oades. There were black label maxells that I had some occasional head loading problems with the D7 but never with the green label ones. I never had an issue with either in my DA20s.
Are you repacking the tapes before recording? I know that there have been quite a few people who reported fewer loading errors when they FF'd then RW'd the DAT completely (on a home deck) before using them in the field. I did that for a while but I didn't do it religiously and it didn't seem to make a difference in my D7. I had more issues from shell design changes and as a result I switched between maxell and sony several times. It might be worth a try.
If I were in your position, I would send back those 90m tapes and get 60m tapes. I can't recall when they stopped making D7s but that deck may be 10 years old and who knows how many hours. I ran 90m in my D7 dats for about 8 years but then I started having some issues loading 90m dats. I switched to 60m dats and my problems went away.
Also, if your deck has not been serviced in a while, send it to prodigital and get a routine service. An alignment and lubrication can't hurt.