Logstash 7.2 file input plugin network path wildcard didn't produce any out

Hi guys!
Please, help. I have a remote file storage with thousands having 10mb average size text files. I'm using this code:

input {
file {
path => "//foldername/**/*.dat"
start_position => "beginning"
}
}
output {
file {
path => "C:/foo/foo.txt"
}
}

Logstash was started successfully and repeats flush cycle. Java is starting load network on Logstash startup. But Logstash doesn't open output file to write incoming data for more than 5 hours. When I'm using in path

//foldername/name1/name2/*/*.dat

it works and with

//foldername/*/*/*/*.dat

it doesn't. I have three level depth with random folders names name1, name2 and name3 that I can't predict. Over the internet this paths are correct in the ruby glob meaning. --debug run didn't represent bugs.
Is there any workaround?

As far as I know there are potentially some known issues with reading from remote file storage, which is documented in the file input plugin docs.