Handling hex files with MSB set in base64 format becomes faulty in handling process

[M4k5]

Hi,

I am currently working on a project where a manually generated hex file is used. There are cases where the MSB of some bytes are set as shown in Figure 1 as an example. 

This file then gets converted to a base64 string for usage in the Flow which looks like this:

First String:

8GVzdDEyMw==

In my Flow I then combine this String with another base 64 String by converting both to binary:

Second String:

QWRkb24=

As an output I get an base64 string which is combined:

Output String:

77+9ZXN0MTIzQWRkb24=

When trying to reconvert this combined base64 string back into hex I get unexpected hex values which do not represent the inserted hex file:

This problem only occured when setting an MSB in the hex file.

Maybe there is a conversion problem in Power Automate or I am unaware of something I am doing wrong.

Thanks already!

Maks

[M4k5]

Does nobody has any idea on how to fix this?