Error with contact forms on website

Since Friday all contact forms changed in code language on our website. It wasn’t possible to fill in one of the contact forms. The code looks like here below:

{9e1ae90a92dfe0e64a516f515339f1df9a37d7cf9b62d04062b0c0559607cbf2}21 – Naam: {9e1ae90a92dfe0e64a516f515339f1df9a37d7cf9b62d04062b0c0559607cbf2}21

In the plugin I see this same code. I tried to start making the fields again, but somehow I can’t save these changes.

Can anybody tell me why this happened and how we can solve this issue? Last week our site change to https. At the moment we are using another form maker plugin, so visitors still can use the form. But we would like to use the plugin from WD, if possible.