I am learning to deal with this material with the 0.25 nozzle.
At the beginning I had problems with very long retractions (about 20cm or more, nearly as if I was changing the material) each time the printer began to extrude.
I solved that thanks to the community, as I read that the problem could be caused by too low temperatures and too fast speeds. I tweaked the profile and finally I could get a smooth print. But this was with retraction off: I turned it off to make the printing easier and get rid of a possible cause of problems.
Finally, I turned retraction on as it is needed to avoid stringing over disconnected zones of the model. Unfortunately, the extra long retraction problem returned again, this time doing it each time a simple retraction is programmed (even in the first retraction after extruding a little material and then beginning to print the skirt), causing grinding and under extrusion, and ruining the printing.
I have tried reducing the speed and length of the retraction by changing the parameters in MATERIAL.TXT. I think in UM2+ it is controlled by this file and not from CURA (more of this in: https://ultimaker.com/en/community/19700-what-are-the-various-parameters-in-the-materialtxt-file). But the abnormal retractions continue.
I have changed back to PLA with the 0.4 nozzle to check if it is a SW or HW problem, but retractions work fine here, so I think it should be something related to the characteristics of the ApolloX material and the retraction parameters but I don't know what to tweak next.
Any ideas? Thanks!