我也遇到这个问题，运行一百个用例之后，就全部报错了。打印堆栈如下

[debug] [JSONWP Proxy] Proxying [POST /element/7E1A2A05-66F0-4704-BEDC-0488F0D4BB3E/clear] to [POST http://localhost:8100/session/C9E177C9-91C4-4311-BF82-C173328A183B/element/7E1A2A05-66F0-4704-BEDC-0488F0D4BB3E/clear] with no body[debug] [JSONWP Proxy] Got response with status 200: "{\n \"value\" : \"Error Domain=XCTDaemonErrorDomain Code=14 \\"Timed out waiting for key event to complete\\" UserInfo={NSLocalizedDescription=Timed out waiting for key event to complete}\",\n \"sessionId\" : \"C9E177C9-91C4-4311-BF82-C173328A183B\",\n \"status\" : 13\n}"
[error] [MJSONWP] Encountered internal error running command: Error: An unknown server-side error occurred while processing the command.
at JWProxy.command$ (/Applications/Appium.app/Contents/Resources/app/node_modules/appium/node_modules/appium-base-driver/lib/jsonwp-proxy/proxy.js:176:15)
at tryCatch (/Applications/Appium.app/Contents/Resources/app/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:67:40)
at GeneratorFunctionPrototype.invoke as _invoke
at GeneratorFunctionPrototype.prototype.(anonymous function) as next
at GeneratorFunctionPrototype.invoke (/Applications/Appium.app/Contents/Resources/app/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:136:37)
at
[info] [HTTP] <-- POST /wd/hub/session/5c99dab6-5692-49b4-b6ea-4ef8c6e09941/element/7E1A2A05-66F0-4704-BEDC-0488F0D4BB3E/clear 500 14751 ms - 238