The problem:

Some UTF symbols are rejected to be saved by t5memory, e.g. \u0003
t5memory replies with the following error

{"ReturnValue":-1,"ErrorMsg":"Error in xml in source or target!"}

https://en.wikipedia.org/wiki/Valid_characters_in_XML

Solution:

Since we need to be able to save such segments to t5memory we need to convert them to internal t5 format, something like t5 tag and then convert back on export, fuzzy or concordance.