WordPress will sometimes do some funny business with the content on your site. Maybe it likes to reformat your table content or adjust your text to something that you didn’t do. Disabling the visual editor can help if you have any customization that breaks because of the visual editor.
Luckily it’s so easy to do I could probably cover it in a single picture:
In the admin area, just click “Users” -> “Your Profile”, and then near the top there’s a checkbox to “disable the visual editor when writing”. And then make sure to go to the bottom of the page and update the changes.
Just make sure you know why you’re making this adjustment to your site, and keep a note of why. Undoing this can cause things to break in your site so make sure you have a backup.