The Bitcoin testnet is behaving in really unexpected ways (this is on the Bitcoin side, has nothing to do with the IC). There are frequent difficulty resets and block surges which make it much more challenging to stay in sync with the tip of the chain and we also see some of the explorers that we are following to check whether we are in sync to struggle. This extra load is adding contention on the subnet which makes execution rounds slower and everything working at a slower pace. So we end up with mainnet being affected.
We’re working on disabling syncing testnet to fix the immediate problem with mainnet becoming available on and off (which is the case for the last few hours) and then we’ll look into a more long term solution to have testnet be available again.