It seems that you send the result of your note/ controller (0/1) on your "plug" message, and not on your "bypass".

Also, "bypass" mutes effect and echoes input to output, as says the help file. You'd better use "disable $1", no ? in case you don't use the fx, you don't have direct audio going through with "disable".

By the way, if the name of your vst includes some blank spaces, you should put it between quotes in your messages, otherwise your vst~ just gets the first element of your message. Ex : plug "GRM Bandpass Stereo.vst".

You can send a standard message (with spaces) through [tosymbol] and it'll put the quotes for you, which can help in some cases.

Thanks you for all your help, it really helps :)