The problem:
I spawn a TNTPrimed using the Bukkit API and then I set the fuse ticks using function: setFuseTicks(60);
At the beginning I want to add that this problem doesn't occur in any version of Minecraft, except the 1.8, where the tnt fuse ticks seems to remain default 80 ticks (I didn't check 1.7 minecraft version, because I am not planning on using it).
I ran into this problem using a LunarClient on which I enabled a mod that allows me to see the time remaining to the tnt explosion, which was wrong (it was counting from 4s to 1s, insted of counting from 3s to 0s).
It turned out that when I extend the fuse ticks to e.g. 200 ticks, tnt disappears in the player's client after 4 seconds (80 ticks), and the explosion appears after the set time (200) in the same place, where the tnt was before.
In my opinion, this situation is caused by Via not sending the ENTITY_METADATA packet to the 1.8 client or sending with missing data about the fuse ticks for TNTPrimed in that packet.
Via plugins:
ViaVersion-4.1.1
ViaBackwards-4.1.1
ViaRewind-2.0.2 (in ViaRewind-2.0.3-SNAPSHOT the problem still exists)
viarewind-legacy-support-1.4.1
Steps to reproduce the behavior:
Login on 1.8.9 client, the server is (in my case) Paper 1.16.5
Spawn a TNTPrimed and change its fuse ticks to e.g. 200 ticks
TNT disappears too early for the set fuse ticks, the blast itself appears at the right moment
Expected behaviour:
TNT should disappear on explosion (like in newer clients, e.g. 1.9), then the fuse time in LunarClient's mod will probably be correct.
Barvalg
commented
2 years ago 
-15%20commit(s)%20behind%20master-yellow?style=flat-square){kind=icon}
-5%20commit(s)%20behind%20master-yellow?style=flat-square){kind=icon}
-11%20commit(s)%20behind%20master-yellow?style=flat-square){kind=icon}
The problem: I spawn a TNTPrimed using the Bukkit API and then I set the fuse ticks using function: setFuseTicks(60); At the beginning I want to add that this problem doesn't occur in any version of Minecraft, except the 1.8, where the tnt fuse ticks seems to remain default 80 ticks (I didn't check 1.7 minecraft version, because I am not planning on using it). I ran into this problem using a LunarClient on which I enabled a mod that allows me to see the time remaining to the tnt explosion, which was wrong (it was counting from 4s to 1s, insted of counting from 3s to 0s). It turned out that when I extend the fuse ticks to e.g. 200 ticks, tnt disappears in the player's client after 4 seconds (80 ticks), and the explosion appears after the set time (200) in the same place, where the tnt was before. In my opinion, this situation is caused by Via not sending the ENTITY_METADATA packet to the 1.8 client or sending with missing data about the fuse ticks for TNTPrimed in that packet.
Via plugins: ViaVersion-4.1.1 ViaBackwards-4.1.1 ViaRewind-2.0.2 (in ViaRewind-2.0.3-SNAPSHOT the problem still exists) viarewind-legacy-support-1.4.1
Steps to reproduce the behavior:
Expected behaviour: TNT should disappear on explosion (like in newer clients, e.g. 1.9), then the fuse time in LunarClient's mod will probably be correct.
Screenshots Not applicable in this situation.
ViaVersion Dump: https://dump.viaversion.com/034776b0b92e2e82da10646dc9e9fe81aa066df5f315b7f711e37d8b400192bb
Additional server info I am using BungeeCord.
Checklist (mark with [X] to check):