steps for reproduction:
on 1.16.3 client connect to 1.12.2 carpet server
place strips of redstone dust
in some places when placing/breaking dust client will crash
fabric version: 0.9.3+build.207
list of enabled mods:
AFKPeace-1.16.2-4.4.0
antighost-1.16.2-fabric0.17.2-1.1.2
appleskin-mc1.16-fabric-1.0.11
audiooutput-1.16.2-0.0.3
autoconfig1u-3.2.2
Blur-1.0.7-1.16.2[fabric]
CustomSelectionBox-5.0.2
fabric-api-0.21.0+build.407-1.16
fabric-console-1.0.1-1.16.3
fabric-language-kotlin-1.4.0+build.1
headdowndisplay-1.0.1+1.16
itemscroller-fabric-1.16.2-0.15.0-dev.20200812.031004
KronHUD-1.0.0-beta-1.16.2
litematica-fabric-1.16.2-0.0.0-dev.20200812.031039
malilib-fabric-1.16.2-0.10.0-dev.21+arne.1
minihud-fabric-1.16.2-0.19.0-dev.20200815.144501
modmenu-1.14.6+build.31
multiconnect-1.3.30
no-potion-offset-1.0.1-unstable
ReAuth-1.16-Fabric-3.9.0
servux-fabric-1.16.1-0.1.3
slight-gui-modifications-1.3.0
slightlyvanilla-1.0.9+1.16.2
statushud-1.1.0
tellme-fabric-1.16.2-0.8.0-beta.1
tweakeroo-fabric-1.16.2-0.10.0-dev.20200812.031359
twitchchat-0.8.2b
Xaeros_Minimap_20.23.0_Fabric_1.16.3
XaerosWorldMap_1.11.0_Fabric_1.16.3

Can you send a screenshot of the contraption causing the crash, and which part of it you are updating?

ve vere making a contraption vith ray yesterday on his stream, and i vas making a clock
so i place dust, second dust, crash

exact place and seed, the one i point onto is the one , caused crash
if place dust on the other side of further one game also crashes