I figured out what the problem was. Ostensibly, it is still a bug. I'll update the title.
Someone in our world built a long ice road, but instead of using real ice / packed ice, he used Frost Walker. This created a long list of pending ticks, to determine if it was going to melt. Attached is the PendingTicks NBT list for chunk (15, 15, tag=51). The ice road goes within the X=15 chunk for quite a long way, and everywhere the ice road exists, there's massive redstone lag. Now that I've deleted all the ice in an offline world, all of the redstone lag is gone.
Ostensibly, frosted ice (especially just a 2-wide path, therefore 32 blocks per chunk) shouldn't create THAT MUCH lag.
MyndFyre
I figured out what the problem was. Ostensibly, it is still a bug. I'll update the title.
Someone in our world built a long ice road, but instead of using real ice / packed ice, he used Frost Walker. This created a long list of pending ticks, to determine if it was going to melt. Attached is the PendingTicks NBT list for chunk (15, 15, tag=51). The ice road goes within the X=15 chunk for quite a long way, and everywhere the ice road exists, there's massive redstone lag. Now that I've deleted all the ice in an offline world, all of the redstone lag is gone.
Ostensibly, frosted ice (especially just a 2-wide path, therefore 32 blocks per chunk) shouldn't create THAT MUCH lag.