When experiencing bugs with the xfce4-power-manager component, your way of helping things getting fixed is to report a bug about it in bugzilla.
Note: For this you will need to have/create an account.

• [Bug 12755] Battery charging/full charged notification spamming (2019/07/19 19:26)
• [Bug 15683] Lowest brightness is 0 (black screen) (2019/07/06 21:01)
• [Bug 15180] screen remains blank on any activity (2019/07/03 12:20)
• [Bug 15151] Unable to override logind lid open/close handlers (2019/07/03 12:00)
• [Bug 15197] [patch] xfpm-backlight-helper reads wrong file for brightness (2019/07/01 00:36)
• [Bug 15658] Standby with lockscreen resume : no lock screen, screen stay black, power button shutdowns computer (2019/06/30 16:01)
• [Bug 15634] Brightness keys Fn+/Fn- do not work. (2019/06/23 18:40)
• [Bug 12062] Screen brightness - increase number of increments (2019/06/19 16:21)
• [Bug 15483] Exhausted battery caused freezing (2019/06/17 01:35)
• [Bug 14687] Screen dims while playing when playing back video (2019/06/04 05:13)
• [Bug 15470] xfce4-power-manager - notifications timeout is hardcoded / not managed by xfce4-notifyd (2019/05/29 03:22)
• [Bug 15486] [Suggestion] Add support for suspend when swap is turned off, but the partition given in the kernel command line. (2019/05/28 04:53)
• [Bug 15300] Laptop lid action not respected (2019/05/27 21:57)
• [Bug 15444] Change systray/system tray to notification area (2019/05/22 00:07)
• [Bug 15387] xfce4-power-manager-settings segfaults in g_type_check_instance due to upower's untimely auto removing USB UPS (maybe) (2019/05/11 21:10)
• [Bug 14716] Power manager is not blank screen (2019/05/11 12:20)
• [Bug 14864] my laptop never powers off (2019/05/11 12:18)
• [Bug 15111] xfce4-power-manager blocks screensaver (2019/05/11 12:18)
• [Bug 15363] Low power pop-ups do not disappear after plugging in (2019/05/05 11:23)
• [Bug 15158] Logout window focusses "Cancel" by default AND/OR add reaction time delay for usage (2019/05/01 22:43)

If your bug/problem has not been reported before, report a new bug. Please ensure that you disclose any information that might be relevant for developers reading the bugreport, e.g. what distribution you're using, what package-version of xfce4-power-manager or related Xfce libraries etc. To report a new bug, go here.