Cannot display default template after switching to custom

Refer to the Template Hierarchy to help understand what’s going on here.

When you create a custom page template, it is identified as such by the header within the file, not by filename. But you’ve also named the file following the page-{slug}.php format, and as you can see in the Template Hierarchy, WordPress looks for the template named page-services.php for a page with slug services, if no custom template is assigned. In your case, they’re the same file.

Rename your custom page template file so it doesn’t clash with other template naming formats and this problem will disappear.