Q: When I mute poly~ with gbr.ola~ in it, it creates a delay effect, as if it's constantly looping its current buffer.
A: Nothing wrong with FTM :-). I'm terribly sorry, just learned something new in Max, really thought I know pretty much everything about poly~, using it all the time, so thought it must've been ola~. It appears though that one cannot use send~/receive~ inside/outside poly~ when muting. (Laurens Van der Wee)
More Info: Indeed, muting a [gbr.ola~] is equivalent to a [gate] before before [gbr.ola~]. Moreover, if you put your [gate] in the [poly~] (higher as possible), and use a single [gbr.ola~] outside of the [poly~], you may gain a lot of processing power. In any case, as Norbert says, you should avoid that the different instances within the [poly~] modify the same data (copy first).
(And if you want to avoid outlets within the [poly~], you can simply use [send] and [receive]; and you can use a list for the samples vector, delay, and channel.) (Jean-Philippe Lambert)
Source: http://listes.ircam.fr/wws/arc/ftm/2011-04/msg00003.html