Why is the rejection rate fluctuated?

What is the rejection rate?
The mechanism for a mining pool is that the pool continues to send out calculation tasks to miners, and miners submit results to the pool. But sometimes when network delay occurs, miners' submissions during the period won’t be admitted by the pool as it has gone invalid. Rejection rate refers to the invalid submissions against the total. 

What is the normal range of rejection rate? What should I do if it is out of the range?
The normal range of rejection rate is within 3%. If the rejection rate fluctuated a lot, it may be caused by network instability. Please check the following:

1. Network connection

2. Overheated mining rigs and the temperature of mining machine 
The hashrate and rejection rate will also be affected by high temperature of the mining machine, especially in the hot summer. The temperature in the screenshot below is basically normal. Different mining machines have different adaption to the maximum temperature, and it is within normal range when the temperature is below 90-100. The specific needs to be confirmed according to different models.

3. Firmware issues
Some miners may have a general high rejection rate due to firmware issues. In this case, you can consult manufacturer of the mining machine for assistance. 

If this issue still persists even after the miner is configured correctly and the network connection is stable, please submit a ticket.

Where can I check the rejection rate?
1. Enter https://www.viabtc.com and then select the [pool].

2. Enter [Pool] page to find [Hashrate Chart]. You may choose to display the hashrate and rejection rate in "10-Min", "1-Hour" and "Daily".

Y-axis to the left represents the hashrate corresponding to the blue curve in the chart, while Y-axis to the right represents the rejection rate corresponding to the black curve in the chart. Apart from paying attention to the curve, please be aware of the horizontal value.