Plugin loaded, tags file regenerated, but :echo tagfiles() outputs [] in certain file

[yurikoif]

Describe the bug
For a random certain file, it appears that the plugin is loaded and the tags file is regenerated once I enter vim, but the tags file is never loaded into vim to be used. Using g:gutentags_trace=1 in the case does not produce any error, nor produces anything different than in a normal case.

Steps to reproduce

1. access certain random file in the project
2. :echo tagfile(), gets []; try ctrl+[, fails
3. but it works on almost every other file in the project

Share your setup

• ubuntu 18.04
• Exuberant Ctags 5.9~svn20110310
• Are you using g:gutentags_cache_dir? YES

Post the logs

• Run :let g:gutentags_trace = 1.
• Reproduce the bug.
• Run :messages and show the messages that Gutentags posted.
• does not produce any error, nor produces anything different than in a normal case (on almost every other file in the project).

Additional context
the problem happens on different projects, in each case of which there is a certain file that causes the failure while all other files work just fine.

[yurikoif]

finally found out it is due to wrong setups in viewdir.