Sharp Inner Corner Cuts Not Completing - FC7000MK2-130

So I've got an older FC7000MK2-130...thing is a workhorse for the most part, but on and off I've had difficulty with sharp inner corner cuts not completing. It's usually only an issue on inner corners less than 45 degrees. Sometimes it'll look like it's cut, but it's just not cut deep enough, other times it fully skips 1/16"-1/8" of the cut line into the corner. I've never been able to come up with a definitive answer why it does this. I've tried changing settings slightly, cleaning blades, new blades...nothing seems to completely alleviate the issue. Again, it doesn't do this all the time, but it does it a lot of the time. I've got 72 24" logos with tons of these inner corners to cut and following along with an X-acto to complete the corners as I weed is getting old.

If anyone has ANY input as to what might be the cause of this and what I can do to avoid it, I'd sure appreciate it.

 

Yeah, the type of vinyl doesn't seem to make much difference. The only vinyl this doesn't seem to be an issue with is reflective, but I use a special blade and obviously very different settings for reflective. Probably 80% of the vinyl I cut is Gerber 220/3M High Performance, and the unfinished corner cuts is a problem on that vinyl as well. I've lubed the blade holder, and I always do test cuts before every job to make sure the blade is set just deep enough to get through the vinyl without cutting into the liner. I've had this plotter for some time...bought it new in 2007, I think, and I've never replaced the cutting strip. I thought maybe that might be the issue, but I never do any perf/die cutting (through the liner), so as far as I can tell, the cutting strip is still in great shape. Stumped.

 

Some great tips here, everyone! However, I have to come clean...I made a mistake that I'm almost embarrassed to admit. A few months back my 10+ year old, all plastic blue blade holder broke. The threads on the bottom broke and there wasn't enough thread left to securely hold the tip on. Not wanting to spend $105 on an OEM replacement, I bought a cheap, all-aluminum (should be more durable, right??) blade holder off Amazon for $15. It sucked. Never could get it to cut well. Knowing full well that they are different, just for the heck of it I put the tip from the blue blade holder onto the red blade holder with a 45 degree blade to see what would happen and to my surprise, it actually cut okay. Been running like that for a few months and the only real issue was the incomplete corner cuts. This recent larger job that motivated me to make this post just had way too many sharp corners/incomplete cuts, so I finally did the right thing the other day and dropped the cash on a replacement Graphtec blue blade holder. Wow. I'm still getting the very occasional incomplete corner, but overall, I think it's cutting better than it has in years. Looks like they've improved the design of the holder over the years, so hopefully this one outlasts the plotter itself. (Last time this thing needed any service, which was the only time, the main board fried about four years ago. We had a very difficult time finding anyone to work on it. Parts were basically non-existent, even four years ago. I do realize if this thing craps out it's basically a boat anchor and I'll need to buy a new plotter. Trying to keep this thing alive as long as possible!)

Thanks again for all the input and tips. It's all been filed in my brain bank.