How to repair issue with tmp_custom_compiler.less?

During an upgrade into Sugar 11.0.1 for a client, the sugarcrm.log presented this error:

<<date>> [17365][-none-][FATAL] Exception in Controller: SugarApiExceptionError: lessc fatal error:<br />load error: failed to find tmp_less_custom_compiler.less in /vol/sugar_pro/include/SugarTheme/SidecarTheme.
php:189
Stack trace:
#0 /vol/sugar_pro/include/SugarTheme/SidecarTheme.php(93): SidecarTheme->compileFile('custom')
#1 /vol/sugar_pro/include/MVC/View/SidecarView.php(76): SidecarTheme->getCSSURL()
#2 /vol/sugar_pro/include/MVC/View/SugarView.php(150): SidecarView->preDisplay(Array)
#3 /vol/sugar_pro/include/MVC/Controller/SugarController.php(350): SugarView->process(Array)
#4 /vol/sugar_pro/include/MVC/Controller/SugarController.php(298): SugarController->processView()
#5 /vol/sugar_pro/include/MVC/SugarApplication.php(124): SugarController->execute()
#6 /vol/sugar_pro/index.php(27): SugarApplication->execute()
#7 {main}

Upon looking at the <<instance url>>/rest/v11_8/login/marketingContentUrl?static=false location in the browser, this error pops up:

{"error":"no_method","error_message":"Could not find a route with 2 elements"}

An attempt to refresh the cache is not resetting the error initially. In researching this error, we found that some have deleted the custom.less file altogether to reset the build of necessary files. Is there a better or safer option?