Is it safe to use pt-online-schema-change in a multimaster environment?
The logic is more complex.  (Caveat:  This is not a definitive Answer to the Question, just more insight.)


Generally (probably in this case), the triggers should be only on the one machine.
RBR replicates the effect of inserts/etc, not the actual statements.  That is what is needed on the Slave (aka other Master).
Are you 'writing' to both Masters?  If so, that is a recipe for extra problems; I recommend you stop writing to the other Master while running pt-osc.


Also look into gh-ost, which uses the binlog in tricky ways.  (Obviously, you have the binlog turned on.)