After printing the resulting negatives on Ilford Galerie I am a bit less frustrated. They print nicely on Grad 2 but need considerably more exposure than Agfa MCC with 75M filtration, about a full stop more, though both papers are ISO P 400. My conclusion is that I need extra filtration with the MCC to compensate for the general stain and more exposure with the Galerie to print through it. I know, the stain should not affect printing times but it obviously does.

I interpret this as to high overall stain and the logical solution would be to cut shorter on the agitation and reduce aerial oxidation. I will certainly not switch to stainless reels as long as I haven't tried harder to solve this problem with technique rather than equipment.

With respect to contamination I tried the following combinations during the last several months (film, development and agitation all the same):
1. Kindermann stainless (old type): Yellow Pyrocat after use.
2. Jobo 1520 with Jobo-Reels: Ruby red Pyrocat.
3. Jobo 1520 with Hayes stainless reel: Yellow Pyrocat.
4. AP (plastic, comparable to Jobo): Ruby Red Pyrocat.

Number 3 shows that only the plastic-reels could be the culprit not the tanks but these are different reels, some in use for years, some hardly ever used others bought just some months ago. I'm flushing tank, reels and everything with 50C hot water after use and wipe them dry with a clean towel (not a lab-towel which doesn't see the sun but often gets dipped into hypo). Contamination? Very unlikely. I have long enough experience in a field where it is much more troublesome and know how to avoid it and what to look for.

To me it seems that my kind of agitation introduces to much air into the developer when using plastic reels and I could either change the reels or the agitation. I would prefer the to do the latter.
Would 10s initial agitation, followed by 3 gentle inversions every minute for 12min be a good starting point for 400TMY in 1+1+100 at 21C/70F?