Simon, Neopan 400 is one of the few films from a major manufactuers that will reticulate quite easily. Rodinal with it's free hydroxide is often the culprit because it significantly sftens the emulsion.

Ilford's film hardening is excellent, the last reticaltion I had was at school (late 1960's) using FP3 & HP3 (ex government surplus), I quickly learnt how to avoid it. FP4 & HP4 had significantly better hardening, it took Kodak a time to catch up.

The issue these days is most films are so well hardened people get lax with temperature controls through out the entire process cycle and few remember that wash is part of that cycle, particularly as very few use hardening fixers now.

Ian