docs: Minor updates

README.md

@@ -111,9 +111,11 @@ behavior. It should also be very fast, as it compiles its mapping code to PHP
 files. The problem was error handling. When an error occurred in the compiled
 mappers, it was usually a `TypeError`. It was difficult to debug, and even more
 difficult to resolve the problem, addressing the problem requires the skill of
-working with AST. However, we found that the problems were deployment errors
-(usually forgetting to clear the cache), some edge cases (easy to work around),
-or bugs in the mapper. We did contributed some fixes back to the project.
+working with AST. We found that the problems were deployment errors (usually
+forgetting to clear the cache), some edge cases (easy to work around), or bugs
+in the mapper. It was rare to get an error, but when it happened, it was
+difficult and time-consuming to resolve. We did contribute some fixes back to
+the project.
 
 The second problem was that the mapper was difficult to extend. Adding a new
 transformer requires the skill of working with AST, and there was no option to