Rstudio becomes unresponsive at several occasions

Hello everyone,

several months ago my Rstudio sessions starts to become unresponsive at several occasions. Unfortunately, I have no reproducible example, as there is no example that triggers the problem reliably.
However, today I encountered the problem four times in a row when I tried to use grepl to select certain columns of a data.frame.

My only hope are the logfiles but I don't understand what they mean. Can anybody help me to understand them and maybe to find the - hopefully easy to fix - problem?
The logfiles from today read

08 Jan 2020 12:28:55 [rsession-User] ERROR grep: D:/Programs/RStudio/bin/gnugrep/grep: D:/.../R/.Rproj.user/91495EDD/sources/s-B251C77B/lock_file: Permission denied
|||; LOGGED FROM: void __cdecl rstudio::session::modules::find::`anonymous-namespace'::GrepOperation::onStderr(const class rstudio::core::system::ProcessOperations &,const class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > &) C:\jenkins\workspace\IDE\windows-v1.2\src\cpp\session\modules\SessionFind.cpp:411

08 Jan 2020 12:29:09 [rsession-User] ERROR system error 10053 (Eine bestehende Verbindung wurde softwaregesteuert
|||durch den Hostcomputer abgebrochen) [request-uri=/events/get_events]; OCCURRED AT: void __cdecl rstudio::session::HttpConnectionImpl<class rstudio_boost::asio::ip::tcp>::sendResponse(const class rstudio::core::http::Response &) c:\jenkins\workspace\ide\windows-v1.2\src\cpp\session\http\SessionHttpConnectionImpl.hpp:111; LOGGED FROM: void __cdecl rstudio::session::HttpConnectionImpl<class rstudio_boost::asio::ip::tcp>::sendResponse(const class rstudio::core::http::Response &) c:\jenkins\workspace\ide\windows-v1.2\src\cpp\session\http\SessionHttpConnectionImpl.hpp:116

08 Jan 2020 12:37:35 [rsession-User] ERROR grep: D:/Programs/RStudio/bin/gnugrep/grep: D:/.../R/.Rproj.user/91495EDD/sources/s-B251C77B/lock_file: Permission denied
|||; LOGGED FROM: void __cdecl rstudio::session::modules::find::`anonymous-namespace'::GrepOperation::onStderr(const class rstudio::core::system::ProcessOperations &,const class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > &) C:\jenkins\workspace\IDE\windows-v1.2\src\cpp\session\modules\SessionFind.cpp:411

08 Jan 2020 12:38:08 [rsession-User] ERROR grep: D:/Programs/RStudio/bin/gnugrep/grep: D:/.../R/.Rproj.user/91495EDD/sources/s-B251C77B/lock_file: Permission denied
|||; LOGGED FROM: void __cdecl rstudio::session::modules::find::`anonymous-namespace'::GrepOperation::onStderr(const class rstudio::core::system::ProcessOperations &,const class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > &) C:\jenkins\workspace\IDE\windows-v1.2\src\cpp\session\modules\SessionFind.cpp:411