contextual filter with taxonomy doesn't produce expected results

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Description of the problem (bug/lack of feature) by example:

Two content types: nodetypea nodetypeb

Two taxonomies: taxa taxb
- taxa is attached to nodetypea, taxb is attached to nodetypeb - (as fields on each type respectively)

Two views: viewa viewb (page views)

viewa:
format - fields (with settings)
filter criteria - content type = nodetypea
-
page path - taxonomy/term/%
-
contextual filter - Content: Has taxonomy term ID
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viewb:
format - teasers
filter criteria - content type = nodetypea
-
page path - taxonomy/term/%
-
contextual filter - Content: Has taxonomy term ID
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The result of the above is that contextual filter appears to ignore that is should operate within the scope of the content filter criteria.

I haven't been able to figure out how, if possible, to tell the contextual filter that it should only apply to taxa in viewa and only to taxb while in viewb.

In the very real world scenario above, because of the two different sets of format settings and node filter criteria, a single view to output the taxonomy matching content wouldn't work.

(might there be an entirely different approach to generating output that is:
- from a single node type (with a specific type of formatting (as definable in a view)
plus
- that content of that single node type and formatting criteria on a given taxonomy term

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The end result is that only one of the two views is operable, and the operable view overrides any content from the other view, and displays content from the overriding view regardless.

Upon testing, when one of the two views is disabled, the other works correctly. When both are enabled, one of the views completely overrides output from the other apparently based upon executing everything related to the path.

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I tried building the contextual filter based on the url alias (generated by pathauto) rather than the underlying raw path, but Views doesn't appear to have a way to deference from the taxonomy term-name to the taxonomy-id in the contextual filter settings.
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It would surely be helpful if a Views / Taxonomy interaction expert could provide some insight about this problem.