resharper-unity: `Copying assembly from 'Temp/Assembly-CSharp.dll' to 'Library/ScriptAssemblies/Assembly-CSharp.dll' failed` when attached to Unity

Unity fails to compile changes with this error when Rider is attached to Unity for debugging.

Copying assembly from 'Temp/Assembly-CSharp.dll' to 'Library/ScriptAssemblies/Assembly-CSharp.dll

Unity 2018.3.0f2 with the IncrementalCompiler 0.0.042-preview.31 package installed.

JetBrains Rider 2018.3 EAP
Build #RD-183.5047.25, built on December 14, 2018
Rider EAP User
Expiration date: January 13, 2019
JRE: 1.8.0_152-release-1343-b26 amd64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Windows 10 10.0