Why is there an unexpected replacement of text with a template?

Question

Google Apps Script

Wrote a script for automatic data replacement. When checking, it turned out that when writing in the DEAL | cell, all sorts of rubbish begins to happen. Who can explain why?

Answer 1

• With a high probability, the problem is in the vertical line of the template.
  
• Another problem may be inadequate code that does not show how the replacement string is formed. It looks like the pattern is partially replaced.