# fdMonitor only works sporadically **URL:** \ **Category:** Legato Application Framework\ **Created:** [February 22, 2023, 12:44pm UTC](https://forum.legato.io/t/fdmonitor-only-works-sporadically/6438 "2023-02-22T12:44:44Z")\ **Posts on this page:** 1\ **Showing post:** 39
**Author:** ![HudriWudri](https://avatars.discourse-cdn.com/v4/letter/h/a6a055/32.png) [@HudriWudri](https://forum.legato.io/u/HudriWudri)\ **Post date:** [March 16, 2023, 10:27am UTC](https://forum.legato.io/t/fdmonitor-only-works-sporadically/6438/39 "2023-03-16T10:27:50Z")
Finally we found the issue. It had two reasons: 1. Something got corrupted heavily as described here: [fdMonitor only works sporadically - #37 by HudriWudri](https://forum.legato.io/t/fdmonitor-only-works-sporadically/6438/37). Please have a look at that stuff because this **must not happen!!!**. From my point of view there’s something deeply wrong if actions like that corrupt something permanently. 2. Once again, the device which sends UART data, sent data to early, meaning before the Sierra’s UART was ready. If Sierra’s UART was not ready before data was received, the UART didn’t function properly anymore (no data was being received). Hence, the watchdog stabilized after a while (as mentioned here [fdMonitor only works sporadically](https://forum.legato.io/t/fdmonitor-only-works-sporadically/6438)). So sometimes the device just crashed (as described here [Kernel BUG at /usr/src/kernel/kernel/time/timer.c:806! - #19 by HudriWudri](https://forum.legato.io/t/kernel-bug-at-usr-src-kernel-kernel-time-timer-c-806/6386/19)) if data was being received at the same moment as _open_ was called or it just didn’t work sometimes if data was being received before _/dev/ttyHS0_ was ready. **This also must not happen!!!** Please have a look at this stuff and even more important: **Please update the kernel! It is - as mentioned [here](https://forum.legato.io/t/fdmonitor-only-works-sporadically/6438/18) - already 7 years old!** Linux: Linux swi-mdm9x28-wp 3.18.140 #1 PREEMPT Tue Aug 3 08:17:34 UTC 2021 armv7l GNU/Linux Legato: 19.11.6\_af84a308b18c93dd4f3ae40f63c9bc67 --- _[View the full topic](https://forum.legato.io/t/fdmonitor-only-works-sporadically/6438)._