Bug description and reproduction steps

On connecting to the server we are having client crashes that claim the uteamcore is not installed. The uteamcore is installed.

Log files and Screenshots

Mod File: useful_backpacks-1.18.1-1.12.1.92-SNAPSHOT.jar
Failure message: Mod usefulbackpacks requires uteamcore 4.0.0.201-SNAPSHOT or above
Currently, uteamcore is not installed
Mod Version: 1.12.1.92-SNAPSHOT
Mod Issue URL: https://github.com/MC-U-Team/Useful-Backpacks/issues
Exception message: MISSING EXCEPTION MESSAGE
Stacktrace:
at net.minecraftforge.logging.CrashReportExtender.lambda$dumpModLoadingCrashReport$7(CrashReportExtender.java:72) ~[forge-1.18.1-39.0.10-universal.jar%2390!:?] {re:classloading}
at java.util.ArrayList.forEach(ArrayList.java:1511) ~[?:?] {}
at net.minecraftforge.logging.CrashReportExtender.dumpModLoadingCrashReport(CrashReportExtender.java:70) ~[forge-1.18.1-39.0.10-universal.jar%2390!:?] {re:classloading}
at net.minecraftforge.client.loading.ClientModLoader.completeModLoading(ClientModLoader.java:183) ~[forge-1.18.1-39.0.10-universal.jar%2390!:?] {re:classloading,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft.lambda$new$1(Minecraft.java:553) ~[client-1.18.1-20211210.034407-srg.jar%2386!:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.Util.m_137521_(Util.java:409) ~[client-1.18.1-20211210.034407-srg.jar%2386!:?] {re:classloading}
at net.minecraft.client.Minecraft.lambda$new$2(Minecraft.java:547) ~[client-1.18.1-20211210.034407-srg.jar%2386!:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.gui.screens.LoadingOverlay.m_6305_(LoadingOverlay.java:135) ~[client-1.18.1-20211210.034407-srg.jar%2386!:?] {re:classloading,pl:runtimedistcleaner:A}
at net.minecraft.client.renderer.GameRenderer.m_109093_(GameRenderer.java:875) ~[client-1.18.1-20211210.034407-srg.jar%2386!:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft.m_91383_(Minecraft.java:1040) ~[client-1.18.1-20211210.034407-srg.jar%2386!:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.Minecraft.m_91374_(Minecraft.java:660) ~[client-1.18.1-20211210.034407-srg.jar%2386!:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at net.minecraft.client.main.Main.main(Main.java:205) ~[client-1.18.1-20211210.034407-srg.jar%2386!:?] {re:classloading,pl:runtimedistcleaner:A}
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?] {}
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?] {}
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?] {}
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?] {}
at net.minecraftforge.fml.loading.targets.CommonClientLaunchHandler.lambda$launchService$0(CommonClientLaunchHandler.java:45) ~[fmlloader-1.18.1-39.0.10.jar%2351!:?] {}
at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37) [modlauncher-9.0.7.jar%2340!:?] {}
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:53) [modlauncher-9.0.7.jar%2340!:?] {}
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:71) [modlauncher-9.0.7.jar%2340!:?] {}
at cpw.mods.modlauncher.Launcher.run(Launcher.java:106) [modlauncher-9.0.7.jar%2340!:?] {}
at cpw.mods.modlauncher.Launcher.main(Launcher.java:77) [modlauncher-9.0.7.jar%2340!:?] {}
at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:26) [modlauncher-9.0.7.jar%2340!:?] {}
at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:23) [modlauncher-9.0.7.jar%2340!:?] {}
at cpw.mods.bootstraplauncher.BootstrapLauncher.main(BootstrapLauncher.java:90) [bootstraplauncher-0.1.17.jar:?] {}
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?] {}
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?] {}
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?] {}
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?] {}
at io.github.zekerzhayard.forgewrapper.installer.Main.main(Main.java:57) [ForgeWrapper-mmc3.jar:mmc3] {}
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?] {}
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?] {}
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?] {}
at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?] {}
at org.multimc.onesix.OneSixLauncher.launchWithMainClass(OneSixLauncher.java:210) [NewLaunch.jar:?] {}
at org.multimc.onesix.OneSixLauncher.launch(OneSixLauncher.java:245) [NewLaunch.jar:?] {}
at org.multimc.EntryPoint.listen(EntryPoint.java:143) [NewLaunch.jar:?] {}
at org.multimc.EntryPoint.main(EntryPoint.java:34) [NewLaunch.jar:?] {}

Used minecraft version

1.17.x

Used forge version

39.0.10

Used mod version

1.12.1.92-SNAPSHOT

Things got wiped unfortunately but it may have been an HD issue.

Seems like you do not have uteamcore installed. Please add this version of uteamcore to the mods list on the server and the client: https://www.curseforge.com/minecraft/mc-mods/u-team-core/files/3583977

As stated uteamcore is installed already. Strangely this may actually have something to do with extreme reactors not uteamcore. It sounds like something is crashing the client and this causes the call to uteamcore from useful backpacks to fail.

Well crash you provided clearly states, that uteamcore is missing. I need more information to better undestand why it is happening. Can you please attach the debug.log files of the client and the server?