I just had troubles with graph windows too after connecting/reconnecting several monitors. One of them 4k.
The solution I found was to backup "HWiNFO64.INI".
Then Deinstall HWiNFO.
Then opening RegEdit and navigate to: "HKEY_CURRENT_USER>Software>HWiNFO64"
Deleting the whole HWiNFO64 branch...