Johan,
I have been running a script tool (.bat) for SSH and it has been connecting to my switch over 66,000 times and i am not seeing your issue but we are trying putty as well. We will keep you posted.
66595 Opening ssh session 66595A on 10.58.196.241 Passed
66595 Closing ssh session 66595A on 10.58.196.241 Passed
66596 Opening ssh session 66596A on 10.58.196.241 Passed
66596 Closing ssh session 66596A on 10.58.196.241 Passed
66597 Opening ssh session 66597A on 10.58.196.241 Passed
66597 Closing ssh session 66597A on 10.58.196.241 Passed
66598 Opening ssh session 66598A on 10.58.196.241 Passed
66598 Closing ssh session 66598A on 10.58.196.241 Passed
66599 Opening ssh session 66599A on 10.58.196.241 Passed
66599 Closing ssh session 66599A on 10.58.196.241 Passed