Fix deadlocked engine in RPC #1442

Job	Run time
Build (x86_64-pc-windows-msvc)	7m 56s
Build (x86_64-pc-windows-msvc)	7m 56s
Build (aarch64-pc-windows-msvc)	7m 55s
Build (aarch64-pc-windows-msvc)	7m 55s
Build (x86_64-apple-darwin)	7m 23s
Build (x86_64-apple-darwin)	7m 23s
Build (aarch64-apple-darwin)	5m 23s
Build (aarch64-apple-darwin)	5m 23s
Build (aarch64-apple-ios)	6m 42s
Build (aarch64-apple-ios)	6m 16s
Build (aarch64-apple-ios-sim)	8m 43s
Build (aarch64-apple-ios-sim)	6m 55s
Build (x86_64-unknown-linux-gnu)	4m 7s
Build (x86_64-unknown-linux-gnu)	4m 7s
Build (aarch64-unknown-linux-gnu)	5m 26s
Build (aarch64-unknown-linux-gnu)	5m 26s
Build (aarch64-linux-android)	3m 35s
Build (aarch64-linux-android)	3m 37s
Build (armv7-linux-androideabi)	3m 50s
Build (armv7-linux-androideabi)	3m 32s
Build (x86_64-linux-android)	3m 39s
Build (x86_64-linux-android)	3m 42s
	2h 6m 51s

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