itsTyrion

IMO, the ideal solution would be to not unload the server RP at the start of configuration phase, but at the end, if either no new 
ClientboundResourcePackPacket was received or the hash does not match (RP changed).

Unless I'm missing something, this would allow for either setting a new resource pack during configuration phase, not setting any and have it unload, or keeping the previous one loaded.

Can confirm. To provide a bit more context, this applies to every server-network with more than 1 Minecraft server software instance, connected via some type of proxy, usually BungeeCord, Velocity or Gate.

While this does not apply to using only the vanilla server.jar, it is a pretty common setup to offer different gamemodes and/or spread higher player counts.

Still an issue in 1.19.4. It happens 99% of time for me

That moment when even a modern Ryzen 9 CPU is not enough to circumvent this issue completely if the treasure is futher away. Not with PaperMC either. Only pregenning more blocks or disabling works ._.