After banging my head to solve this, finally found the issue.
For JS minimization, if another plugin uses inline jquery (quite common for dynamic script generation), then it will fail with a jquery not found. There are two possible approach (that I am aware of) to fix this :
- switch js minimization to 'manual'. fine tune it to avoid any minimization on the relevant section (i.e. <head>)
- OR change the plugin code to not use inline js