I tried to submit a proposal grandpa.note_stalled(1000, 917920) to see if it unblocks finalization, but it says the block state has already been discarded, so it won’t work. Maybe it will work if someone else with an archive node does it, but I don’t know what proportion of the nodes must have the blocks for this call to work.
If you do it, don’t forget to wrap it into upgrade_origin.dispatch_as_root, as only root can call this.
/// Note that the current authority set of the GRANDPA finality gadget has stalled.
/// This will trigger a forced authority set change at the beginning of the next session, to
/// be enacted `delay` blocks after that. The `delay` should be high enough to safely assume
/// that the block signalling the forced change will not be re-orged e.g. 1000 blocks.
/// The block production rate (which may be slowed down because of finality lagging) should
/// be taken into account when choosing the `delay`. The GRANDPA voters based on the new
/// authority will start voting on top of `best_finalized_block_number` for new finalized
/// blocks. `best_finalized_block_number` should be the highest of the latest finalized
/// block of all validators of the new authority set.
/// Only callable by root.
Maybe it stopped because there were not enough grandpa voters online during an entire session. This problem should happen less often with more smiths.