[markerClusterGroup] loses all markers

I have just updated a site to version 3.5.6 and all the markers on my map have disappeared at all scales. Reverting to version 3.5.5 has restored them.

The shortcode I am using is:

[markerClusterGroup feat=”iconUrl” strings=”https://…/wp-content/uploads/2022/03/visited.png,https://…/wp-content/uploads/2022/03/mentioned.png,https://…/wp-content/uploads/2022/03/birthplace.png,https://…/wp-content/uploads/2022/03/grave.png” groups=”…visited these places.,…mentioned these places.,…birthplace,… grave”]

Removing the shortcode restores the marker points but without the clustering and the selection option.

Can you please investigate?