Tests run is complete with no successful results

[testhorse]

I am using webpagetest npm package, to run tests on my 10 web pages one after the other.
command used :
webpagetest test <page1_url> -k <api_key> -v
webpagetest test <page2_url> -k <api_key> -v
.
.
webpagetest test <page10_url> -k <api_key> -v
All the tests were running fine for last 3 months.

Recently, some of tests started failing from 17th April 2020.
Some of the tests are passing and some are failing, this is very random.

When I checked the report url, it looks as follows:

Even after trying : webpagetest restart <test_ID> nothing happens.
When tried manually from the result page, the tests gets restarted and works fine.

Looking for help. Would appreciate. Thanks.