Sorry to hear the issue. I’ve checked your ticket #210890, and our support team will follow up with you soon to investigate the issue further and provide a solution.
Both mine came off. One was the bolt holding the spindle and the other was the screws holding the cap. The spindle bolt that was still on was pretty loose.
I found parts and put it all back together, but I’m worried about it happening again. It was luck finding the blades and caps in the yard (though not rocket science as I could tell where the grass stopped cutting).
I tightened everything but good, but I’m afraid of overtightening or using loktite so that the screw will strip or break off.
I’m also kind of surprised they are coming loose so readily, it’s just from vibration? Anyone find a way to keep them on but not cause the breaking/stripping problem?
I personally think the cap is contributing to not being able to lock them down well enough and I think no cap is the way to go, but I’m keeping with them until it happens again
I’d open a ticket so they can evaluate it and possibly send you the update cap design. I personally haven’t had an issue with either of mine and I have the original caps.
I also have not had an issue with my blades coming loose since I received the new caps and blades, but I did use Loctite and followed the torque spec Yarbo provided earlier in this post.
And my mower has gotten jammed several times by branches over the last couple of weeks.
Looking at this picture I was wandering if anyone has fitted those pro single blades to their M1 unit? The bracket looks the same to me. And if it’s missing the correct holes then most likely the aluminum bracket is not expensive. Or it’s not hard to make the correct holes to the existing M1 bracket. Drive shaft looks the same as on M1…
And yes, I know the motors have different power output. Everything else on a naked eye looks the same
People have made adapters to mount the blades.
Great.
I also was asking for a friend
I opened a ticket yesterday without response yet, but it’s not an “emergency” situation I guess. I put the newer/larger cap back and 3D printed another one, found a new bolt and screws and put it back together. It’s holding up for now.
And FWIW, for all those complaining that they bought the M1 and couldn’t upgrade to the Pro, when the blades fell off (this is the 2nd time) having the M1 as a spare is very useful, so I’m glad to have both and didn’t “upgrade” and lose the M1 in the process.
Well, it happened again. I noticed an odd mowing pattern on a job, pulled the mower from the core, and sure enough, a blade was missing. Fortunately I was able to recover the blade, the cover, and one screw, all intact. It looks like the screws had just come loose again and the blade came off. There was some minor damage to one of the back skirts, but otherwise everything looks ok. And the other blade was fine, not loose at all.
While the thread lock seemed to help initially it clearly didn’t “solve” it. I would now say that there’s something that needs to be improved in the design, so I’m going to start inspecting those blades every week from now on.
Posting as a heads up to others that use the straight blades.
Just curious what your cut height is? I’d open a ticket so they can be aware and maybe offer a solution. It really shouldn’t be coming loose. Mine haven’t so far with a year of use.
They are sending me new caps and screws for a second time. The one time the blades stayed secure was without the cap, just screwed to the spindle.
Something must be missing in the equation for this to be happening so often…lock washer, compression washer, something 
Originals were all plastic, cheap, can’t tighten down good, temp affects plastic too much. Replacements are better have metal inserts in them to tighten down on.
I keep the cut height at 2.7" or higher, which is the recommendation, correct? The odd thing to me is that the screws are coming loose. So far the caps have been fine, with no cracks. I wonder if I’m just not tightening them enough.
Yes, that is a reasonable cutting height. If you’re using loctite on them, then I would say you may not be tightening them enough. Make sure to put loctite across the top 5 threads of the screw near the screw head. Are your caps the old style full plastic or have the metal in them? If metal, you can definitely crank a little harder.
I’m still running with no caps. My blades stay tight without any loctite use. The caps seem to be a problem.
Could you please provide pictures of the blade and the cover on the problematic side? This will help us further investigate the issue.