1.20.2 error spam in SSP

[megaraichu]

When running in 1.20.2 in singleplayer survival the game lags heavily, almost unplayable, but the mod is working. However latest.log shows repeating large errors. All the errors appear to be identical, and it throws these errors every few seconds. The lag is so bad that it causes other mods to fail to be detected, such as TechReborn. Can this be fixed?

[11:22:26] [Server thread/WARN]: Exception loading entity:
net.minecraft.class_148: Loading entity NBT
at net.minecraft.class_1297.method_5651(class_1297.java:1947) ~[client-intermediary.jar:?]
at net.minecraft.class_1299.method_17839(class_1299.java:550) ~[client-intermediary.jar:?]
at net.minecraft.class_156.method_17974(class_156.java:514) ~[client-intermediary.jar:?]
at net.minecraft.class_1299.method_5892(class_1299.java:549) ~[client-intermediary.jar:?]
at net.minecraft.class_1299.method_17848(class_1299.java:636) ~[client-intermediary.jar:?]
at net.minecraft.class_1299.method_17842(class_1299.java:587) ~[client-intermediary.jar:?]
at net.minecraft.class_1299$1.method_31490(class_1299.java:610) ~[client-intermediary.jar:?]
at java.util.ArrayList$ArrayListSpliterator.tryAdvance(ArrayList.java:1602) ~[?:?]
at net.minecraft.class_1299$1.tryAdvance(class_1299.java:609) ~[client-intermediary.jar:?]
at java.util.Spliterator.forEachRemaining(Spliterator.java:332) ~[?:?]
at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:762) ~[?:?]
at net.minecraft.class_5579.method_31835(class_5579.java:203) ~[client-intermediary.jar:?]
at net.minecraft.class_3218.method_31426(class_3218.java:1528) ~[client-intermediary.jar:?]
at net.minecraft.class_3898.method_31413(class_3898.java:714) ~[client-intermediary.jar:?]
at net.minecraft.class_3898.method_31415(class_3898.java:733) ~[client-intermediary.jar:?]
at net.minecraft.class_2818.method_12206(class_2818.java:442) ~[client-intermediary.jar:?]
at net.minecraft.class_3898.method_17227(class_3898.java:738) ~[client-intermediary.jar:?]
at com.mojang.datafixers.util.Either.lambda$mapLeft$0(Either.java:162) ~[datafixerupper-6.0.8.jar:?]
at com.mojang.datafixers.util.Either$Left.map(Either.java:38) ~[datafixerupper-6.0.8.jar:?]
at com.mojang.datafixers.util.Either.mapLeft(Either.java:162) ~[datafixerupper-6.0.8.jar:?]
at net.minecraft.class_3898.method_20460(class_3898.java:726) ~[client-intermediary.jar:?]
at java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:646) ~[?:?]
at java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:482) ~[?:?]
at net.minecraft.class_3900.method_17634(class_3900.java:62) ~[client-intermediary.jar:?]
at net.minecraft.class_1255.method_18859(class_1255.java:156) ~[client-intermediary.jar:?]
at net.minecraft.class_3215$class_4212.method_18859(class_3215.java:564) ~[client-intermediary.jar:?]
at net.minecraft.class_1255.method_16075(class_1255.java:130) ~[client-intermediary.jar:?]
at net.minecraft.class_3215$class_4212.method_16075(class_3215.java:573) ~[client-intermediary.jar:?]
at net.minecraft.class_3215.method_19492(class_3215.java:282) ~[client-intermediary.jar:?]
at net.minecraft.server.MinecraftServer.method_20415(MinecraftServer.java:766) ~[client-intermediary.jar:?]
at net.minecraft.server.MinecraftServer.method_16075(MinecraftServer.java:754) ~[client-intermediary.jar:?]
at net.minecraft.class_1255.method_5383(class_1255.java:115) ~[client-intermediary.jar:?]
at net.minecraft.server.MinecraftServer.method_16208(MinecraftServer.java:738) ~[client-intermediary.jar:?]
at net.minecraft.server.MinecraftServer.method_29741(MinecraftServer.java:671) ~[client-intermediary.jar:?]
at net.minecraft.server.MinecraftServer.method_29739(MinecraftServer.java:263) ~[client-intermediary.jar:?]
at java.lang.Thread.run(Thread.java:833) ~[?:?]
Caused by: java.lang.NoSuchMethodError: 'void net.minecraft.class_2658.(net.minecraft.class_2960, net.minecraft.class_2540)'
at net.minecraft.class_1309.mdf4c102$flycommand$lambda$markNoFallDamage$0$0(class_1309.java:6733) ~[client-intermediary.jar:?]
at java.util.ArrayList.forEach(ArrayList.java:1511) ~[?:?]
at net.minecraft.class_1309.markNoFallDamage(class_1309.java:6733) ~[client-intermediary.jar:?]
at net.minecraft.class_1309.handler$zpj000$flycommand$readNbt(class_1309.java:6726) ~[client-intermediary.jar:?]
at net.minecraft.class_1309.method_5749(class_1309.java:807) ~[client-intermediary.jar:?]
at net.minecraft.class_1308.method_5749(class_1308.java:466) ~[client-intermediary.jar:?]
at net.minecraft.class_1296.method_5749(class_1296.java:113) ~[client-intermediary.jar:?]
at net.minecraft.class_1429.method_5749(class_1429.java:103) ~[client-intermediary.jar:?]
at net.minecraft.class_1321.method_5749(class_1321.java:52) ~[client-intermediary.jar:?]
at net.minecraft.class_1453.method_5749(class_1453.java:478) ~[client-intermediary.jar:?]
at net.minecraft.class_1297.method_5651(class_1297.java:1938) ~[client-intermediary.jar:?]
... 35 more