Could you share a photo example of one of the emails?
Are you using our ReCaptcha extension to help prevent spam submissions? Also do you have Akismet enabled. And finally are you mapping your Inbound Form fields to Lead Fields using the field mapping system?
Yes, as far as I can tell the emails that have broken HTML are not recorded in the leads while the emails that are intact are. These started coming in like this after the event sign up was due to close and we receive approx. 15-20 a day like this. I have sent some tests myself and they made it through ok and the email also looked intact.
There is a possibility timeouts or memory shortages are happening. Will you let me know your Hosting provider and I’ll see what I can discover to increase available resources and decrease the change of breakage.