Nextcloud 14.0.1 & gpxedit 0.0.9: "App is not compliant"

occ app:check-code gpxpod

Analysing /var/www/html/apps/gpxpod/controller/comparisoncontroller.php
 1 errors
    line  135: OC_App - Static method of private class must not be called
Analysing /var/www/html/apps/gpxpod/controller/utilscontroller.php
 1 errors
    line   96: OC_App - Static method of private class must not be called
Analysing /var/www/html/apps/gpxpod/controller/pagecontroller.php
 1 errors
    line  201: OC_App - Static method of private class must not be called
App is not compliant

What does this mean? Thank you!