I don't know if I'm just dumb or did anything wrong or whatever, but when I go into the Replay Viewer, I get greeted with:
"Error loading entity tracker: decoding"
And when I try to put a keyframe in, I get greeted by:
"---- Minecraft Crash Report ----
// This doesn't make any sense!
Time: 8/14/17 4:32 AM
Description: Failed to load entity tracker, pathing will be unavailable.
java.io.IOException: decoding
	at com.replaymod.replaystudio.io.ReplayInputStream.readPacket(ReplayInputStream.java:142)
	at com.replaymod.replaystudio.util.EntityPositionTracker.loadFromPacketData(EntityPositionTracker.java:128)
	at com.replaymod.replaystudio.util.EntityPositionTracker.load(EntityPositionTracker.java:87)
	at com.replaymod.simplepathing.gui.GuiPathing.lambda$startLoadingEntityTracker$6(GuiPathing.java:496)
	at com.replaymod.simplepathing.gui.GuiPathing$$Lambda$142/1967305056.run(Unknown Source)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalStateException: Packet "ServerEntityTeleportPacket" not fully read.
	at com.github.steveice10.packetlib.tcp.TcpPacketCodec.decode(TcpPacketCodec.java:44)
	at com.replaymod.replaystudio.studio.protocol.StudioCodec.decode(StudioCodec.java:42)
	at com.replaymod.replaystudio.io.ReplayInputStream.readPacket(ReplayInputStream.java:140)
	... 5 more
A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------
-- System Details --
Details:
	Minecraft Version: 1.12
	Operating System: Windows 10 (amd64) version 10.0
	Java Version: 1.8.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 301698960 bytes (287 MB) / 657641472 bytes (627 MB) up to 1060372480 bytes (1011 MB)
	JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
	IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 99
	FML: MCP 9.40 Powered by Forge 14.21.1.2387 13 mods loaded, 13 mods active
	States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
	UCHIJA	minecraft{1.12} [Minecraft] (minecraft.jar) 
	UCHIJA	mcp{9.19} [Minecraft Coder Pack] (minecraft.jar) 
	UCHIJA	FML{8.0.99.99} [Forge Mod Loader] (forge-1.12-14.21.1.2387.jar) 
	UCHIJA	forge{14.21.1.2387} [Minecraft Forge] (forge-1.12-14.21.1.2387.jar) 
	UCHIJA	replaymod-compat{1.12.1-2.0.0-b8} [Replay Mod - Compatibility] (replaymod-1.12.1-2.0.0-b8.jar) 
	UCHIJA	replaymod-render{1.12.1-2.0.0-b8} [Replay Mod - Render] (replaymod-1.12.1-2.0.0-b8.jar) 
	UCHIJA	replaymod-replay{1.12.1-2.0.0-b8} [Replay Mod - Replay] (replaymod-1.12.1-2.0.0-b8.jar) 
	UCHIJA	replaymod{1.12.1-2.0.0-b8} [Replay Mod] (replaymod-1.12.1-2.0.0-b8.jar) 
	UCHIJA	replaymod-editor{1.12.1-2.0.0-b8} [Replay Mod - Replay Editor] (replaymod-1.12.1-2.0.0-b8.jar) 
	UCHIJA	replaymod-extras{1.12.1-2.0.0-b8} [Replay Mod - Extras] (replaymod-1.12.1-2.0.0-b8.jar) 
	UCHIJA	replaymod-online{1.12.1-2.0.0-b8} [Replay Mod - Online] (replaymod-1.12.1-2.0.0-b8.jar) 
	UCHIJA	replaymod-recording{1.12.1-2.0.0-b8} [Replay Mod - Recording] (replaymod-1.12.1-2.0.0-b8.jar) 
	UCHIJA	replaymod-simplepathing{1.12.1-2.0.0-b8} [Replay Mod - Simple Pathing] (replaymod-1.12.1-2.0.0-b8.jar) 
	Loaded coremods (and transformers): 
LoadingPlugin (replaymod-1.12.1-2.0.0-b8.jar)
  
	GL info: ' Vendor: 'ATI Technologies Inc.' Version: '4.5.13476 Compatibility Profile Context 22.19.171.1024' Renderer: 'AMD Radeon (TM) R9 390 Series'"
So, could anyone shed some light on the situation? That would be appreciated.