HIK Connect regularly getting bell images not snapshot images.

My HIK Connect (Android APP) new notifications regularly fails to receive a camera snapshot image but get bell images instead.

I've seen other posts on this issue but they seem to go off to discuss email / SMTP settings. I'm not using email and it's not configured - just HIK-Connect.

My equipment is a DS-7616NI-I216P with 5 local POE DS-2CD2383G0-I cameras and 4 LAN POE DS-2CD2383G0-I cameras.
DS-7616NI-I216P Firmware V4.21.008 build 190625 ... [Configuration\Network\Advanced...

HIK Connect regularly getting bell images not snapshot images.