Sam Lockwood

Siavash Tehrani
Just a couple of things to try.
1) Do you have Core Performance Boost enabled for your processor in your BIOS? If so, try disabling that.
2) I haven't used the Steam version of Houdini but I assume it saves preferences in the same place as the regular version. Try renaming your houdini18.5 preferences folder under My Documents so a new one is generated on launch. FYI this is not a folder that Houdini will remove when you uninstall it.