I am using this code to embed an iframe:

For some reason when saving the K2 article a dash is added after the ''i'' in ''iframe like this:

Then it does not work. I have removed the iframe ban from the TinyMCE editor. Please help. I did not have this issue before joomla was updated.

Hello,

This is not related to K2.
Another extension possibly a security or an optimiser is changing the structure of your HTML.

Hi. Thanx for the help. Do you have any clue on how I can find out what the problem is?

This is a trial and error procedure.
You need to deactivate security and performance plugins one by one to see which one is causing this issue.