I have an ender 3 v3 plus and I’ll get the same issue every once in a while on the first layer. Sometimes I just restart the print and it works. \o/

Adhesion and bedmesh calibration should solve the explosions/under extrusion in far back. The stringiness/ bad line-line adhesion is from bad z level calibration.

I think you already have your answer, but let me elaborate a bit.

The places in the middle where the filament is missing - those places are either dirty or too high.

The area in the back where the filament is sticking, but isn’t filling the area correctly, those areas are too low.

Most likely cause for both is the build plate on an Ender just isn’t perfectly flat. You can try to adjust it to get it closer to being level. But I’ve always found I’ll have sections that just aren’t right. And so, I just don’t print on those sections. Find the areas that do print well, and locate your prints there.

Last note - try putting down a layer of painter’s tape. I find that helps tremendously with both of the points you’re fighting.

Things that have worked for me:

• your bed is probably not level, i installed self leveling on mine ($30 but well worth it)

• if its adhesion, try a glue stick. It looks like a PEI sheet but that alone was not enough for me. My routine is: wash with soap and water, spray 90+% IPA (before bed is heated) and wipe with microfiber (paper towel leaves flakes behind), then apply gluestick before printing

• maybe check your bed is warm enough/preheat for longer to allow the whole bed to get to temp, though i doubt this is the case but it doesn’t hurt to try

• for your first layer: slower speed, higher nozzle temp, higher bed temp

I would check that the print bed is heating evenly. Everyone has mentioned cleaning, that’s definitely a good start, too. But it looks like bands where it’s not sticking. From the image’s perspective, about 1/3 up is a band of poor adhesion, and then at the far end of the plate. IDK how the heating elements are designed, but that could be a. Issue. Otherwise the build plate is warped in almost an “S” shape. Some leveling will help, but not fix a warped bed.

Also, the material deposition looks very thin in general. Make sure the z-step is set correctly, slow down the first layer print, and make sure the temperatures of the bed and hotend are right.

I have an older printer with a warped bed and basically brute force the adhesion with a slightly thicker base layer and then normal layers after that.