template variables in email signature versioning?

Hi all. Thanks in advance for any help.

We're creating a link like so in our Unsubscribe HTML Email Setting

<a href=https://customer.com/manage?id={{Lead.SyncID}}>

This normally works well. However, sometimes, we're seeing emails go out without substituted ids. Rather, they look like so:

<a href=https://customer.com/manage?id={{Lead.vSyncID_1553704896}}>

Can anyone help me figure out what is going on, and how I fix this?

Thanks!

Message was edited by: Earl Jackson trying to clean up the display