Fix deadlocked engine in RPC #1440

Job	Run time
Build (x86_64-pc-windows-msvc)	6m 31s
Build (aarch64-pc-windows-msvc)	7m 37s
Build (x86_64-apple-darwin)	5m 26s
Build (aarch64-apple-darwin)	10m 21s
Build (aarch64-apple-ios)	8m 17s
Build (aarch64-apple-ios-sim)	9m 27s
Build (x86_64-unknown-linux-gnu)	3m 49s
Build (aarch64-unknown-linux-gnu)	6m 1s
Build (aarch64-linux-android)	4m 22s
Build (armv7-linux-androideabi)	3m 34s
Build (x86_64-linux-android)	3m 42s
	1h 9m 7s

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