Monoprice i3 Mini (Wanhao i3 Mini clone) sudden persistent under-extrusion (maybe)?

[LudivousKain]

First off, I'm new here and thus is my second attempt at posting my issue to ask for help. The first attempt was made several days ago and, after getting a message saying it needed to be approved by a mod, nothing happened..

In short, I bought the printer mentioned in the subject for cheap. It's my first 3D printer and I'd always wanted one, so I thought it was fate telling me the time was now!

I initially had bed adhesion issues, but corrected them by changing the print surface, leveling it ~20 times in a row and before every print, and learned the importance of glue sticks ^_~

For the last 3 months, everything was fantastic. I love this little clunker, even though there are FAR better options available. As a hobbyist, I was very satisfied.

That all changed about 3 weeks ago, when I started getting severe warping on every print, and more recently a rather severe case of what appears to be under-extrusion. No change was made, as one day I was printing fine and the next day things started to separate between layers and are full of holes. I'll attach pics when I get home.

So far, I've tried 4 different filaments (2x petg and 2x pla) from two brands, adjusted the printing temperature, adjusted the layer height, adjusted print speed, and even completely disassembled the entire device to ensure its free from clogs and 'rough spots' with all the moving parts (including the filament feeder and filament tube).

I'm really at a loss for what to try next. I'm hesitant to replace the entire hot-end, as it looks like it'll cost almost as much as I paid for this entire printer. And if that's the case, I might as well replace the entire thing. Though I'm not entirely convinced that the issue will be corrected with that...

The filament looks like it's being extruded correctly when I use the "add filament" option in the printer's menu, so I'm thinking that the physical movement is somehow causing the filament to retract? I'm open to suggestions and feedback here, as I really REALLY love 3D printing and want to continue turning all sorts of ideas into real physical objects...

Apparently the mobile version of this site doesn't want me to edit pictures into this thread, so I'll post them below. As for the Cura settings, everything not mentioned below was left at the default/autocalculated value for "Fine" quality:

Temp: 220C
Speed:25mm/s
Initial layer height: 0.3mm
Layer Height: 0.06mm
Line Width (for all in it's section): 0.4mm
Infill: 50%

For the plate adhesion section, I typically use a "raft," whose width/margin is set as high as it can without exceeding the area of the print platform, but not to exceed 15mm. I use the raft in combination with frequent leveling and glue stick application to overcome the apparent "normal" bed adhesion issue with this printer, and it usually works wonderfully for me. Until the above issue started, anyway...