Got weird bug in most recent stable HeidiSQL. The SSH tunnel option is somewhat erratic on two separate computers, one with 64-bit Windows 10 and one with 64-bit Windows 7.
When I try to start a SSH tunnel connection to our database, from time to time, I get a prompt for plink.exe that it wants my passphrase. This prompt only has "OK" button option, no methods to enter the passphrase.
I've entered the passphrase into connection's SSH Tunnel tab (to "Password" field).
To make it more weird, every now and then, the connection succeeds, without me changing anything in the settings. But 9 out of 10 times, I get the plink.exe dialog and connection failing as it cannot find database at localhost (as it should).