How to determine the compression method?

Question

Mathematics

Good day. There is a problem with defining the data encoding method. There are several records of the file (pieces with compressed information are highlighted).
Here is the compressed character sequence EFCAEFCEFC

Here is 413 characters U

Another transmission of 413 characters U

The compressed data has a clearly visible prefix 0x00E3E5 and suffix 0x0000XXXXXXXX (the last 4 bytes of the suffix change from transmission to transmission). Compression of random data is worse than sequences of identical characters. So far, this is all that has been installed. I would appreciate any help and guidance on a solution.
Thanks in advance.