Well, the first thing I would check is how tightly sitting the boards in the connectors, well, I would not miss the case of wipe the contacts of the board with isopropyl alcohol (only with it you need to work in protective gloves - if you have at least the slightest scratch on the skin for a long -healing wound - it corrodes the skin like acid, and see it does not get on the plastic - it dissolves many plastics) - there are few where and what kind of and what kind of and what kind of and what kind of and which Has the dirt hit?
Electronics is the science of contacts, and at least 95% of the problems are to blame.
With Wi-Fi, at least it is worth picking up a slot in which he will not conflict with other boards, but it is better to change TP-Link to something else. Here is a photo of the board of their cable router 100-Base-T. Yeah, only from 8 MB of 7.9 MB, rolled up on the board, OS uses OS, and on the routing tables, DHCP, the DNS and the buffer remains 100 KB RAM and, as a result, at a connection speed of up to 10 MB/s it still works, and already at 15 - 16 MB/s, if one pair of ports is installed, the remaining three are waiting for its completion. The contraption is cheap, I bought it myself as it was urgent, but there was no time to look for something decent, but like everything from this office "we save on matches!". Buy better the Intel or Broadcom and TP-Link adapter will definitely not be problems.