Several bugs: getting "Save Failed" when trying to save changes to dashboard, drag and drop no longer works (can't drop), filters won't set and don't seem to work upon use, "Cannot read property 'card' of undefined"

Hello. The title says it pretty clearly. I’m experiencing several issues with my dashboard:

-Getting “Save Failed” whenever I try to save changes on the dashboard (even just changing text in a heading or other small changes)
-Drag and drop no longer works (can drag, can’t drop), and
-Filters won’t set once I select a field from the drop-down menu and don’t seem to work upon use. For one of them, when I selected a field from the drop-down on the chart, it set a DIFFERENT chart to that field for the filter

How can I get help addressing these issues? Thanks

If it’s helpful: one of the issues (the drag and drop one) was experienced at an earlier date on a different dashboard as well. But then it resolved for a while and now is happening again.

EDIT: Additional issue: when I tried to add a new chart to the dashboard, I got the message " Cannot read property ‘card’ of undefined"

While I’m not expert enough to help you those who can will want to know the following: