When performing drawing cleanup, consider the following issues:
If objects have object data, hyperlinks, or SQL links associated with them, drawing cleanup may break these associations. You can control this behavior by selecting a cleanup method that either retains or modifies the original object.
For greater control of the cleanup operation, consider performing one cleanup action at a time and completing one action before moving to another.
To display the extent and nature of the problems in the drawing, use markers for your first cleanup pass.
Start the cleanup operation using small tolerances and review to find out whether the tolerance setting has captured the errors. If the tolerance settings are too low, repeat the cleanup operation with a larger tolerance until the operation recognizes the errors. Be careful when increasing tolerances. If tolerances are set too high, valid geometry can be recognized as errors.