Issue with a Word doc web table row that keeps disappearing

Hello,

I have a rather annoying problem (but it doesn’t prevent me from working) that I’d like to solve with a Word document Word downloaded and opened and edited with office.com (office.com are the WEB applications of the Office suite: Word, Excel, etc... that can be used for free without all the features) in the form of a worksheet (a ready-to-fill sheet in table form when you open the document: see screenshot) : when I bring my paragraph/text as close as possible to the column lines (there is no space between the paragraph and the column line), everything is fine but as soon as this is done and I click inside the column, the line disappears on its own and I have to click again for it to reappear, and it does this every time I click again. Can you help me solve this annoying problem please?

PS: I remind you that I am working on office.com for free and therefore I don’t have all the features and that this table is already created when I download and open the doc, I didn’t build it myself in Word. See screenshot. The problem occurs often but randomly

Thanks in advance.
Link to screenshot :
In the first one the problem does not appear, when I click above the paragraph before the line, the table line stays in place and does not disappear (you can’t see the text but the white space before the table line is there because I didn’t paste the text up to the line) :


On this one, the problem appears, I click above the paragraph just before the line that will disappear when I click on it and when I click again at the same spot it reappears (sorry I know it isn’t very clear but it’s hard to explain clearly, I would have loved to make a video but I can’t):