strange clogs with PET

Hi all! I have this filament, a kind of PET. It is really driving me crazy. It is really a good material, really strong, almost like naylon, but cheaper.
It is really dificult to print with it but I cant figure it out what the problem is exactly.
Reccomended temperature: 230/250
The print starts and sometimes it clogs very quickly, other times it takes minutes, sometimes the print completes with almost no problems.
What I see when printing is that suddenly I hear the noise of the filament being grinded by the hobbed bolt. If I hear that, I can pause the print, retract 1 or 2 mm and resume printing, with no problems at all, and the same will happen again later.
I can figure it out why this happens. I have tried and observed this:

-. I though that my heatbreak was getting too hot. I replaced the fan. Then I also started useing a radial fun. And then I ended useing a BIG radial fan (and believe me, it is big and blows a LOT of air to the cold end). Thinking about this this shouldnt be the problem, since I can eprfectly print with PLA. If the heat break is getting too hot, I should have problems with PLA too, right. But I can print LONG PLA prints with no issue at all.
-. I have read that PET really likes water. I have a chamber where I dry my filament rolls. And I print with them inside the chamber. Humidity inside the chamber is between 10 and 20%. Drying this filament seems to help a lot. If I print with the filament right out of the box, the clogs happen much much more frecuently.
-.I have tried almost anything: low temperature and low speed = seems to help a little, but really dont know how much really helps. Increasing temp till 240/245 and higer speeds (50 mms). This seems to work the best. Clogs still happen when for some reason speed is reduced, like in small perimeters, some small infills. The problem with this setup is that I cant print nice details o models wich require slow printing
I still have not tried increasing the temp to 250 degrees. I kind of refuse doing that because I notices that PET likes to sag and to leak. I have manually extruded at 250 and the filament get really leaky, it leaks a lot.
-. other thing I observed is that problem might be related t back pressure because when the clogs happen at the beginning of the print, it is always when the bed leveling is somehow too close to the noozle. Also, when clogs happens dureing the print, I have learnt to predict them. If I see a surface being finished, or a small infill, it will probably happens because some overextrusion is happening because of the extra material being leaked and I think thaat could be a reason for creating back pressure?
When the clogs happen, if I pull the filament out, the tip of the filament comes out with like 4 mm of an expanded section and if I measure that, that expansion seems to happen exactly in the heat break section (but I think this is somehow normal?)
My printer, prusa 3, is perfectly calibrated, I have a e3d all metal hotend,
Any ideas what is happening here and ho to deal with this PET?

thanks in advance and please feel free to ask any information you think would be usefull to discover the problem.

I've learned to print slow and without retraction with PETG. Maybe you could try a heatbrake with PTFE sleeve inside. ( all metal hotend usually means: no PTFE liner )

If the extruder is slipping and grinding the filament you need more pressure on the idler.

Can you give a link to the filament - I'd be interested to see what it is.

Thanks all for the comments: useing a PTFE heatbreak is not a good option for this range of etmperatures. PTFE starts to break at those temperatures and releases toxic fumes in the process.

The link:

[bpetfilament.com]