Fix deadlocked engine in RPC #1441

Job	Run time
Build (x86_64-pc-windows-msvc)	8m 3s
Build (aarch64-pc-windows-msvc)	8m 6s
Build (x86_64-apple-darwin)	7m 4s
Build (aarch64-apple-darwin)	7m 17s
Build (aarch64-apple-ios)	7m 21s
Build (aarch64-apple-ios-sim)	5m 34s
Build (x86_64-unknown-linux-gnu)	3m 58s
Build (aarch64-unknown-linux-gnu)	6m 2s
Build (aarch64-linux-android)	3m 35s
Build (armv7-linux-androideabi)	3m 46s
Build (x86_64-linux-android)	3m 38s
	1h 4m 24s

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