Using existing hardwired doorbell

All is working except my indoor chime (16VAC) isn't cooperating with the Video Doorbell 3 pushbutton. When pushed, it rings but won't release until about 5-10 seconds later. Chime rings, then hums for 5-10 sec and releases. This doesn't happen if I short the 2 wires together (normal ring) so something is happening when going through Video Doorbell. Again, doorbell transformer is 16VAC so it's in the 8-24 VAC range specified in the manual. Thanks for any help in this matter.