it looks like this could be due to an inline attachment being added in the description on the ALM or Jira side. Connect All does not support in line attachments from ALM to Jira so this could be the cause. This is a common limitation of synchronization tools since attachments are stored differently in various tools.
I am not saying that the entity in ALM and Jira cannot have attachments the problem is when an attachment is put ''in line'' in the description field.
As a test you can try the following
Create a defect in ALM, in the description, when typing in the description click the ''insert image'' button, this will let you put an image ''in line'' in the description. Then when synced you will see html in the description on Jira side
Same goes for Jira if you embed a screenshot into the description and sync it to ALM then it may look ok the first time that it gets synced but then when it gets synced back to jira after someone adds to the description in ALM it can have html in the description.
If you create a defect in ALM you should be able to put other formatting in the description and it should work ok, i.e. italics bullet lists, etc. The limitation is that inline attachments are handled differently by both tools and are therefore not supported. A user can instead say ''reference the attached screenshot'' etc to refer to and that is ok, but actually embedding it in the comment/description will cause this html issue.
This also would extend to comments coming between ALM and Jira and any other ''memo'' and ''wiki' fields that you have synced together