Symptoms

The gallery macro throw the following message:

Error trying to draw image gallery org.apache.velocity.exception.ParseErrorException: Encountered "=" at /templates/gallery-dynamic-slideshow.vm[line 64, column 37] Was expecting one of: ... "-" ... "+" ... "*" ... "/" ... "%" ... ... ... ... ... ... ... ... ... 

Cause

The gallery macro is even dysfunctional or disabled. Since there's another gallery macro with the same name, they can be mistaken.

Resolution

1. In User Add-On, enable gallery and gallery-slidshow
2. In System Add-ons/Advanced Macros, enable gallery and gallery web resources system plugin.
3. In User Add-On, disable gallery and gallery-slidshow
4. In System Add-ons/Advanced Macros, disable gallery and gallery web resources system plugin.
5. In User Add-On/Gallery, enable gallery, leave gallery-slideshow disabled.
6. in System Add-on/Advanced Macors, enable gallery, leave galery web sources disabled.