Fix deadlocked engine in RPC #1445

Job	Run time
Build (x86_64-pc-windows-msvc)	7m 30s
Build (aarch64-pc-windows-msvc)	7m 27s
Build (x86_64-apple-darwin)	9m 17s
Build (aarch64-apple-darwin)	9m 54s
Build (aarch64-apple-ios)	7m 38s
Build (aarch64-apple-ios-sim)	7m 29s
Build (x86_64-unknown-linux-gnu)	3m 57s
Build (aarch64-unknown-linux-gnu)	13m 3s
Build (aarch64-linux-android)	3m 59s
Build (armv7-linux-androideabi)	3m 57s
Build (x86_64-linux-android)	3m 36s
	1h 17m 47s

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