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putty go slow

It may not be mail list specific but maybe somebody knows ?
If I connect windows 10 to debian Buster with putty and edit a file.
Usually the little cursor beetles across the screen over the characters
but then sometimes it is noticeably sluggish.
This is probably something to do with the network connection.
Any idea to find out what might cause this sluggardly behavior ?
apologies for off topic but I'm unlikely to join a win10 user group.

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