According to @str4d
“it seems that zcashd is getting stuck in addrman.cpp inside a while (1) {} loop that only exits when a random integer exceeds an increasingly-weighted “selection chance” of a randomly-selected address in a randomly-selected bucket. My guess is that our buckets are much emptier than Bitcoin Core either because our testnet architecture is much more centralised or because there are many fewer participants, and it is therefore taking much longer to satisfy the exit requirements”
So basically this behavior is only present because we have so few participants on the testnet at any given time, bitcartel has developed a work around to hold us over until it goes live.