The teleprovider has to send items using LUA scripting, and it limits how often it does it to keep the script from bogging down performance. In particular, looking at the code it basically iterates down the list of teleproviders in the game, 1 per tick. If you've got a lot of them in a game, it can take a while for it to get through the list. Since each provider chest only has one slot, it limits max throughput of any provider to 1 stack/(total number of providers) tick.
I'm guessing your test world only had the ones you were using for your test setup, while your real map has those plus more elsewhere on the map, making the overall throughput slower.
I'll look into changing how the code works for the next version - it shouldn't affect processing times too much to change it so that it processes more per tick when it needs to, possibly change it so each provider is processed once per second regardless of how many they are (as it is if you've got only one provider, it gets processed 60 times a second).
A future version might switch to using the new linked chest feature, but that would mean redoing a lot of how the telelogistics work - you can't link chests if they aren't the same entity name, and they're always bi-directional, so it'd end up being Provider<->Provider instead of Provider->Beacon. Upside is the inventory management for linked chests is all handled C++ side, so little in the way of performance issues.