Like it or not, I won't be a bit surprised if both of you guys have a bunch of lint packed tightly into the bottom of your phone's charge port*. This is easiest to check by plugging in an Apple Lightning cable and checking to see that the white plastic head is flush with the phone body. If it is not flush, then the port is packed. If it is, then another problem exists.
We use dental picks to clean ports out, because lint can get packed in so tight it
literally feels like plastic until you start to dig it out.
This little "feature" is the cause of 99.9% of the "loose cable" charging issues that we see in the shop, and is a very easy problem to solve with the right tool, i.e. a sharp metal pick. But, be careful when scratching around in there so that you do not tear up the electrical leads.
* 1) You put the phone in your pocket; 2) Lint gets into the port; 3) You plug in the charger; 4) The charger packs the lint into the bottom of the port; 5) Repeat!
Eventually, the lint "pack" gets so thick that the charger and the leads no longer make reliable contact.