What server are you talking about? Are you talking about Spot client or are you talking about some pool?
Difficulty adjusts only based on the time it took to mine last 2 blocks and not based on anything else.
the network server. If SPOT uses only 2 blocks to calculate the difficulty that would explain these jumps.
There are no network servers in peer-to-peer network. There are only nodes: every Spot client is a node of the network and all of them agree on the difficulty change because they all have the same algorithm to calculate it: The target of the block is 70 seconds and for 2 blocks target is 140 seconds: if 2 blocks are found faster than 140 seconds, the difficulty will be adjusted up to compensate proportionally based on the actual time it took to find those 2 blocks and reverse is also true: if it took longer than 140 seconds to find 2 blocks, the difficulty will adjust down, so next two blocks shall be found in 140 seconds