Error after deactivate and re-activate the plugin

Hi,
After updating the plugin to newest version, I deactivated the plugin once to debug another issue, then when I tried to re-activate it, the page stops responding and ended up with the “Too many redirects” browser error, it looks like the page is stuck at “/wp-admin/admin.php?page=mec-intro”, I have to deactivate the plugin to make the whole site work. In the meantime, while the plugin is active, the mysql CPU usage is extremely high over 100%, when I deactivate it, the CPU usage dropped back to normal.

Don’t know if it’s a rare case or common issue, but I look forward to a solution.