When a page contains multiple channel forms on the same page, each with a matrix field; the Add Row button adds multiple rows (1 per channel form on the page it seems.)
Is there any easy way to work around this?
After examining some pseudo-related questions I discovered that multiple instances of the matrix.js were being loaded causing multiple executions upon the Add Row click event. I added include_assets="no"
on channel forms after the first one which prevented the problem.