Short answer to 1. Your z probe offset was wrong.
Short answer to 2. Get an accurate probing of the washers, and having the latest firmware is absolutely crucial.
Not knowing exactly what you started with, but where you appear to know what you’re doing with a machine, I’ll do a quick checklist for getting an unknown machine set up. Who knows what the previous owner did - custom firmware? never update firmware? no reason to leave it up to question.
Start with the latest stable version of Cura LE. (3.6.40 as of this writing) - LulzBot | Cura LE Windows - yes, you can use other slicers, and some have profiles for the Taz 6, but we need a reliable baseline. It will also come with the latest firmware. Speaking of which…
Make sure you’re running the latest official “universal” firmware - 22.214.171.124.13 or higher. Universal just means that it has all the compatible toolheads selectable on the machine itself. After loading the firmware, you will still need to select the proper toolhead from the Toolhead menu on the machine. There is often confusion between the SE and Single Extruder. If your extruder has a massive plastic gear, you’re probably looking at the Single Extruder. If it has e3d hologram stickers on it, it’s probably the SE 0.5.
What print surface is it?
Is it magnetic, black and have a big green octopus and grid? You’ve got the Octograb. It’s awesome.
Is it glass with a lightly frosted plastic coating, with a metal grid visible underneath? That’s the modular print bed. Pretty good.
Is it glass with a lightly frosted plastic coating, with a red heater visible underneath? That’s the standard print bed.
Important part here, is each of these beds sits at a different height relative to the washers.
The octograb is about .3mm higher than the washers (probe offset 0.3mm).
The modular and standard print bed usually sit lower than the washers by about -1.25mm (probe offset -1.25mm).
If your adjustments to the Z take it outside of -1.5 to 0.5 there’s probably something wrong, or you’ve got a third-party bed surface.
The firmware doesn’t take into account your bed surface, so if you’re starting from scratch, you can start with those and adjust as necessary.
If you can provide video of your startup/homing/leveling procedure, that would help the most.
The firmware-executed sequence you should see is:
Lift Z a little, then move to the big metal button.
Move nozzle to, and push the big metal button. The tip of the nozzle should hit almost dead center of the button. If it does not, there is something wrong with the homing of the X/Y (or wrong toolhead selected, but we ensured that was right earlier, right?). Could be something triggering the endstop soon, or the bed is not in the right spot. Follow bed install instructions according to ohai.lulzbot.com to fix this.
Now the commands from the slicer take over:
Heat nozzle to wiping temp. Temp depends on the filament.
Move to wiping pad position.
Heat nozzle to probe temp.
Move to first washer.
Probe washers. So here’s where the lulzbots generally fail. Any bit of plastic (or material from the wipe pad) on the nozzle will wreck the accuracy of your probe. While direct contact is by far the most accurate way to probe, it relies on clean contacts. When one of your contact points is also one used to extrude plastic, it’s not a great system unless the wipe is perfect. If the nozzle is contacting a washer but not stopping on the first washer, and the nozzle is clean, it could be a broken zero sense wire. If it restarts after probing the second/third/fourth washer, it could be that the frame is out of alignment, or your gantry is sagging on one side.
continue the rest of the print