@Teknor I tend to agree something is wrong, but I think it really on depends how many nodes and how often you're sending data.
rpi3 + GPIO nrf24l01 + openhab2 + 8 nodes + packet received, on average 1 / 5s :

top - 06:29:37 up 2 days, 22:33,  2 users,  load average: 0.26, 0.24, 0.19
KiB Mem:    947732 total,   903420 used,    44312 free,   175364 buffers
KiB Swap:   102396 total,     4496 used,    97900 free.   391360 cached Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                                                               
  681 root      20   0  208840  56532  23684 S   8.9  6.0 214:23.60 Xorg                                                                  
  527 root      20   0   39448  21532  11264 S   4.3  2.3  69:34.28 vncserver-x11-c                                                       
 1154 pi        20   0   50548  17628  12196 S   3.0  1.9  64:05.96 lxterminal                                                            
30426 openhab   20   0  441764 197592  14960 S   1.6 20.8 284:18.70 java                                                                  
 2467 root      20   0   20024   2456   2300 S   1.3  0.3  62:55.17 mysgw                                                                 
25634 root      20   0       0      0      0 S   1.0  0.0   0:00.21 kworker/u8:0                                                          
  688 root      20   0   13720   9432   8828 S   0.7  1.0   2:04.96 vncagent                                                              
25855 pi        20   0    5232   2584   2140 R   0.7  0.3   0:00.49 top                                                                   
    7 root      20   0       0      0      0 S   0.3  0.0   9:15.35 rcu_sched                                                             
   78 root     -51   0       0      0      0 S   0.3  0.0   5:16.50 irq/92-mmc1                                                           
  967 pi        20   0   95656  17716  12028 S   0.3  1.9   6:41.87 lxpanel                                                               
    1 root      20   0   24620   4688   2716 S   0.0  0.5   0:13.08 systemd                                                               
    2 root      20   0       0      0      0 S   0.0  0.0   0:00.27 kthreadd                                                              

Hi fahrettine. Good to hear I am not alone, however I felt kind of lonely in here so, even though I really liked the looks of MyNodes, I did a quick popularity survey based on posts and tried Domoticz and my gateway and sensors came right up! I noticed derwish is working on a new project so I am not sure sure of the status of .NET. Good luck, and please do post if you figure something out.

Hi sundberg84. Thank you for the reply.
Currently I just have the 1 ESP8266.
I think I found the issue. There is a a lot written online about the error and what I got from it was the ESP8266 is being asked to do more than it has time to do. Given that I was only transmitting every 10sec I started looking at what might be tying things up. From the MySensors ESP8266 example I had, naively, changed the sleeps to delays, since I did not want it sleeping. I realized that might be killing the ESP8266. So I changed the loop function to run freely and the code to be executed on interval. I have not seen the error since.