Have edited this question in light of further information subsequent to the initial question being posted...
Have Stash 3.0.4 running on EE 3.4.6.
Have migrated an EE2 site that is working fine, to EE3.
Several of the templates are simply a one-line {stash:embed} tag which redirects to one of several shared templates. The redirect templates look like this:
{stash:embed:_resources-cat-index process="start"}
This redirection approach works fine in EE2, but in EE3 the embeds are failing: rather than running the template defined in the embed, an error is displayed of this form:
The following errors were encountered
Stash: the file "/var/sites/e/ee3.2gc.org/system/expressionengine/templates/default_site/stash_templates.group/_wwd-index.html" was not found.
Because the error occurs before a template is loaded, there is no debugging information showing beyond this error message.
I have tried removing all the one other extension that uses the template_fetch_template
method but it makes no difference.
Any ideas what might be a solution?