Extensions application causing error screen when clicking submit button

Hi!
When I go into Applications>Extensions and select an extension, then immediately click the “Submit” button, I get the following error (see below.) This occurs only in some extensions and not all! The error is repeatable for the same extensions, the extensions that don’t have this error never have it.

Does anyone have an idea if there is something enabled on that extension that is causing this problem? Which error log would have the information I need to debug?

FreePBX 15.0.27
Current Asterisk Version: 16.29.1

Exception thrown with message "Unknown App Type "

Stacktrace:
#8 Exception in /var/www/html/admin/modules/restapps/Restapps.class.php:1132
#7 FreePBX\modules\Restapps:getHintByApp in /var/www/html/admin/modules/restapps/Restapps.class.php:1149
#6 FreePBX\modules\Restapps:getHintByAppExtension in /var/www/html/admin/modules/endpoint/functions.inc/functions_digium.php:1303
#5 endpoint_digium_contacts in /var/www/html/admin/modules/endpoint/functions.inc/functions_digium.php:202
#4 endpoint_write_digium_ext in /var/www/html/admin/modules/endpoint/functions.inc/functions_common.php:69
#3 endpoint_write_ext in /var/www/html/admin/modules/endpoint/functions.inc/functions_common.php:352
#2 endpoint_save_extensionHook in /var/www/html/admin/modules/endpoint/functions.inc.php:475
#1 endpoint_core_process in /var/www/html/admin/libraries/components.class.php:469
#0 component:processconfigpage in /var/www/html/admin/config.php:450

/var/www/html/admin/modules/restapps/Restapps.class.php
Arguments

  1. "Unknown App Type "