Sorry guys! I wrote that post too quickly, but I meant that I tried REV 5's (old Amiga 500's what I got from recycle center) "Chinon" brand floppy drive in my primary Amiga 500 (rev 6, what I bought from internet). And same results. As I mentioned in my first post, loading errors shows up only in OFS/FFS filesystem applications. Other works well ex. Lotus 2, Zool etc. what uses custom loaders. Floppy drive makes strange sound, when loading and seems like that the "disk swap" is not working correctly...
My never Amiga 500 (rev 6) what has green power light and yellow floppy light, has Panasonic's FD, what is much worse than the Chinon (in rev 5 what has red power light and green floppy light.) Chinon can handle HD floppies as DDs perfectly, when Panasonic can't read them at all.
I hope that this post was now more understandable than the first one 
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And I have external FD what works fine in Rev6 and I believe that it works too in Rev 5 as the Rev 5's fd won't work the proper way in rev 6, so I believe that Rev5's chinon is faulty.
-Eemil
Okay, sounds like the disk drive is dusty...do you have an air duster or something you can spray it with? Also sounds like the "disk inserted" sensor is acting up...WD-40 does wonders on switches and such things, or just try air dusting that part. There's been a few recent threads on faulty disk drives, so you might want to do a bit of searching as you may find the info you need in there.
A friend of mine had a slow motor on his floppy drive and he replaced it and that fixed it. There's also allignment of heads, but I wouldn't know how to go about altering that.
