what operating system are you on?
If you are on Linux try reinstalling miniconda:
wget https://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh -O ~/miniconda.sh
RUN bash ~/miniconda.sh -b -p ~/miniconda
If you are on windows, make sure Windows Defender or other antivirus is not running.
This is not an R issue, but rather a conda issue. I happened to stumble on it recently: