I have one Writer document always open and about 6 Calc spreadsheets always open which are minimized to the taskbar. If I return to edit any of these several hours later I am unable to do so. I have to close the file and reopen it. These files are in docx and xlsx format.
Is this a bug or am I doing something wrong?
Thanks for any help anyone can offer.
No operating system given nor where files are stored even though this looks like an OS question. Based on the information I will guess that you are using Windows and the files are on a network share accessed through WiFi.
When Windows goes into sleep it drops the WiFi connection; on wake the connection is restored out of order and although you are connected to WiFi it doesn’t work so you need to restart the connection. Even if you don’t need to restart the WiFi connection, you still need to mount the mapped drive again. To do that just open File Explorer and click on the mapped drive to show the folders in the right-hand pane.
BTW, leaving Windows running non-stop and files always open will guarantee that oneday a restart will corrupt something. Keep doing those backups 
Cheers, Al
My apologies for the lack of information. Windows 10 2004 on a desktop. Files are on OS drive in “My Documents”. No WiFi, no network share, no mapped drive. And no sleep mode. Yes, computer is on all the time. I have files which are uploaded on the web frequently as data is dynamically updated. Everything is backed up daily.
I have certainly left Writer documents open for several hours without problem, I would want to test again with Win10 2004, LO 7 to be sure but this week is looking very disjointed.
Are Memory and CPU looking OK when you try and restore the programs?
My documents/spreadsheets don’t send or collect data from web pages. I wonder if it could be the connection.
I left a Win10 version 2004 with LO document (Version7.0.1.2) open for 24hours accidentally yesterday. Document was fine but, curiously, I couldn’t get Dropbox to synch to get last night’s files; I had to reboot to get it moving again. Just before I did that I tried to open a Writer document in the same unsynchronised folder and it took two minutes before it opened. This might be unrelated or it might be a Windows issue.
I am a new user to LibreOffice in the last week. This situation is not consistent so I suspect it may be something else causing the issue such as my anti-virus. This computer is a fairly new build with 16gb of memory and a Ryzen 5 CPU at 3.2 ghz. At time of lock-up CPU is 13% and memory is 34%. Interestingly, the 13% CPU usage is used by the anti-virus. I will continue to monitor this issue. Thanks for your help.