uneven prints and gaps, underextrusions  

the filament is leeking

This sounds like a hardware issue.  Have you changed your nozzle recently?

Cheerio,

RE: uneven prints and gaps, underextrusions

as i wrote i changed the nozzle january 25, because of the leeking and the massive print problems. the initial issue where that my prints does not stick anymore on the plate, i using glue. Second massive strings and the nozzle produces alot of "debris" while printing. and the prints are extremely uneven, as you can see in the picture...i cant practically use the printer vecause the prints looks really horrible, far away from the firstvquality when i bought the mini. 

RE: uneven prints and gaps, underextrusions

Check if your nozzle is properly tightened when hot, but do not overtighten.it because it may cause heat block thread getting damages and this will cause leaks or wobbling nozzle and uneven extrusion.

Please provide more details about the printer age and the components.

RE:

Sorry, I wasn't clear, I meant had you changed your nozzle before the symptoms appeared?  A common cause of leakage is a wrongly installed nozzle.

Pay particular attention to the diagrams at the bottom of this page:

https://help.prusa3d.com/article/changing-replacing-the-nozzle-mini_134235

Poor adhesion is either or both of a dirty build sheet and a first layer 'Z' configuration set too high.

Cheerio,

RE: uneven prints and gaps, underextrusions

The mini is 4 years old, i made in this time 2x nozzle change, heatbreak and hotend, normal maintenance like extruder cleaning, 2x firmware upgrade. all parts are original, no mods. Yesterday i squared the printer and checked the belts.  Because of the massive leekage i changed the nozzle in January after one year. But its still leeking. Tomorrow i will make a testprint again to check if the squaring and belt adjustments had any effect.. 

RE: uneven prints and gaps, underextrusions

did you use brass nozzles or hardened one?

RE: uneven prints and gaps, underextrusions

i use the normal factory brass nozzle, i print only pla. yet another issue appears, layer desintegration, so on one side of the print the wall layer are splitted... this printer drives me crazy, a lot of issues and no idea how can i fix it... 

RE: uneven prints and gaps, underextrusions

Please how us a picture of your nozzle/heatblock assembly from two different angles.

Cheerio,

RE: uneven prints and gaps, underextrusions

Not quite sharp enough to be certain but it appears that molten filament has been running down from the top of the heatblock - please check.

If so the most likely cause is a wrongly installed nozzle.

Pay particular attention to the diagrams at the bottom of this page:  https://help.prusa3d.com/article/changing-replacing-the-nozzle-mini_134235

Cheerio,

RE: uneven prints and gaps, underextrusions

Also check if the nozzle is loose when hot, if it gets loose over time after assembly this usually means damaged threads in the heat block.

In that case it would be better to replace original aluminium one with plated copper/brass. This also helps in minimizing issues with hardened steel nozzles.