NTFS external hdd partition mounted in windows 7 desktop: ok
same partition mounted in windows 10 laptop: ok

windows 10 laptop went into sleep mode
I think i removed the usb drive without usb safe removal (either before/after wakeup)

not sure if windows 7 reported a need to repair the disk when I plugged it in then.

reconnect to windows 10:

windows 10 reports "Path is not accessible. ... file or directory is corrupted or not readable"
can't usb safe remove the drive in windows 10 (reports an unkown error)
disconnect the usb and connect the drive to windows 7 again
windows 7 reports partition needs repair
chkdsk reports only error and correction of Attribut BITMAP of MFT, and Volumebitmap
still partition is accessible without problem in windows 7

plug into windows 10 again, same as above "path is not accessible ..."

searched a bit and found most interesting:
"File system interoperability in multiple boot environments. CHKSDSK / AUTOCHK and unexpected NTFS dirty bit"
File system interoperability in multiple boot environments. CHKSDSK - Microsoft Community

"Windows 8 volume compatibility considerations with prior versions of Windows"
Windows 8 volume compatibility considerations with prior versions of Windows - TechNet Articles - United States (English) - TechNet Wiki

I had the same problem couple of weeks ago, where running chkdsk on windows 10 corrupted the partition soo much that I had to reformat.

I disabled the fast mode shutdown on windows 10 laptop after that.
So this time the problem was caused by standby mode I think

Now my understanding of the issue is:
windows 10 sleep mode / fast mode shutdown will not dismount the external usb drive, but instead make a copy of the $MFT and other metadata

disconnecting the drive from windows 10 - during sleep or without safe usb removal - and connecting it to windows 7 will change the NTFS metadata on the partition.
reconnecting it to windows 10, metadata copy and partition metadata does not match, so windows reports a corrupted ntfs partition?
chkdsk on windows 10 actually makes things worse (like the 1st time it happened) and uses outdated metadata to repair a uncorrupted ntfs parition (I read about this in another forum on my research during 1st issues)
I haven't done a chkdsk on windows 10 though yet, just on windows 7

so the partition is fine, data is fine, on windows 7
windows 10 reports it corrupted.
chkdsk on windows 10 will most likely corrrupt the partition (like it did the 1st time)

how can I make windows 10 accept the external hdd partition again?
some way to clear all windows 10 cached ntfs metadata of the once mounted partition?
make it like the partition was never plugged in?

if no better answer, solution would be:
backup partition in windows 7, plugin to windows 10, chkdsk, probably reformat due to corruption, restore data from backup