Have you been able to resolve the problem? Does rewashing or refixing the film help?
I have encountered something similar / the same this weekend, developing 9x RPX-400 in RPX-D. The emulsion of the DRYED film feels a bit sticky and seems to have white powder (extremely fine, finer than flour) embedded as a kind of drying spots. I gave all the films a final bath in distilled water & surfactant, and I am sure my process & lab is clean enough / water soft enough for not having caused this. All the film has been fresh, procured directly from Maco between September 2016 and January 2017, exposed in December / January 2016. RPX-D has been freshly bought / opened, the Fixer has been open a while (4-6 months), smells a little but it is clear and has behaved perfectly normal in a clearing test and fixing HP5+.
I am not sure about what could have caused this, but maybe the following has contributed:
1.) I have done a rotation development, I am not sure whether RPX-D is suitable for rotation development?
2.) I have used Ilford Rapid Fixer 1+9 for 5 minutes, which is approximately 2,5 times the clearing time. Maybe, this film need a stronger fixer?
3.) 7 of the 9 films were slightly fogged by X-Ray (three times at various airports) and overdevelopment, maybe this had an effect? BTW: Despite of the fogging/overdevelopment, the tonal range & contrast of the pictures is just fine.
I have passed two of the films between my fingers to "facilitate drying", and the powder is in a shape of lagoons of the water spots although the emulsion itself is unharmed. The powder became visible immediately inside the emulsion - the water was clean, so I hang the other films directly and they have a fewer spots.
I have developed another 3 RPX-400 in RPX-D manually (one x-rayed, two fresh). For one I have used the acid stop bath (more spots), the other two were bathed in water only instead of a proper stop. These last two look a little better than the others, yet the emulsion is a bit sticky, too, and there also seems to be the white powder - but thinner. I have furthermore developed 5x HP5+ in Microphen 1+1 which turned out just perfect - nothing strange at all.
I have not tried to print these negatives yet, so I don´t know if this affects during printing.
Any ideas anybody?