Good afternoon Mel and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
We apologize for the inconvenience caused by this glitch.
We are actively working on a fix for this.
Unfortunately, I cannot commit to a release date for a fix at this point.
But you will be contacted as soon as there is one.
In the meantime try adding the following CSS rule to your style.css file or in your Custom CSS metabox: https://theeventscalendar.com/support/forums/topic/map-size-too-small-on-single-event-since-version-4-4-3-updates/#post-1244515
Thank you for your patience as we see this through.
Best regards,
Geoff B.