Clarifications to Vicky's comment:
[try to close BusinesWorks, it locks up and they have to ctl+alt+dele to close the program and run DBRegister to release the stranded tasks.]
This isn't accurate. Workstation doesn't lockup. It displays series of pop-up error messages, after closing BW, to which you have to press "ok" to each, and then it finally says it is "unable to close Business Works", along with various 3006 and 3112 type errors messages. You can log back into Business Works again, on the same pc, right away, even without DBRegister clearing. You can work in Business Works, as long as you stay active. You can close BW without a crash if there's activity, but if the pc is lying idle for longer than 30 minutes (a guess), and you try to close, it crashes. Is there a way to permanently set the session timeout on the server or pc to 1440 minutes (24 hours) to prevent timeout inactivity disconnect? The second pc is in WIFI mode, and has no problems with server inactivity, and never times out. Internet speed 142 mbps. Old location was 100.

Spend 50 bucks, get a 8 port gigabit switch, new cables Cat5e or better, and put all the BW clients and server on the new switch. connect new switch to old switch/router to gain DNS/DHCP and internet access

Chasing down a wireless gremlin is no fun.

Vince

Only 2 workstations. PC in garage 30 feet away, and behind thick walls, is wireless and has had zero problems opening and closing BW. It's not possible to bring Cat5e cables to this workstation. Problem pc is behind a single wall just a few feet from server. The current modem/router next to server, can handle up to 500mbs. We were operating before in a 100mbs with all 5 pcs, all attached by cable, with no problems. Now, it's just 2. Will check with IT rep regarding rest of your suggestion.

We spent $2000 including tech labor, to buy and install individual Netgear 5-port and 7-port gigabit switches hard-wired to each of the individual pc's and mesh modems. The server is connected to a 2-gigabyte router and modem. All three are connected together in a WIFI network, with three individual ASUS Mesh routers. It looks like the problem pc is resolved. BW no longer crashes on exit, simply by changing the System>Power "Screen & Sleep setting", for when to put the device to sleep after inactivity to: "never". There is some latency, but not an intolerable amount, compared to the previous installation, hard-wired with cable, at 100mbs. We're paying for 500mbs but usually getting 140-160.

Glad to hear your BW problems are solved.  Sorry that it was $2k. The PC shutting it self off to standyby mode was enough to cause the connection issue. (POWER SAVING)

As far as your internet is concerned, is it 500 megabit service?   I have 800 megabit service and see 873 Mbps.. remember a small b is bits and a big B is Bytes and a factor of about 10 in speeds ( 8 bits = 1 Byte + overhead) .  I use https://speedtest.xfinity.com/ to check our internet spped. you can search your internet provider's site to see if they have a test, if you don't use Comcast.

EDIT:  another speed test site    Internet Speed Test - Measure Network Performance | Cloudflare

We used this site when we change internet speed (50Mbps  to 800Mbps) and found the router has a mis-configured port (10/100) instead of gigabit (1000) and our speed was well below the expected number.

Vince