Duo LDAP over Watchguard SSL VPN constantly sending authorization prompts

We are testing Duo using a Watchguard SSL VPN connection over LDAP. It connects fine but then at random times we receive authentication prompts. The prompts come even while the user is actively using the computer. If the VPN is left connected while the computer is unattended then we receive multiple prompts and the account gets locked out. We upped the lockout threshold to 99 and received almost 50 prompts overnight. Watchguard support reviewed their logs and are saying the issue is with Duo or our LDAP settings. Has anyone else experienced this issue? Thanks in advance!