Your file name is wrong, it's called "cpu" instead of "gpu".
If you have some errors in HWInfo64 so your overclocking goes too far, maybe the warmup of 0.31f did not trigger the error but that's still a too strong overclocking. Maybe retry from stock frequency then rise back by steps.
I'm not arguing that overclocking is great for these cards, I simply state the fact that on the sapphire rx550 11268-16-20G the latest version is not the best option.
I ran the test on this version of the miner, the launch is possible only with a memory frequency of 1820 MHz, but this is already 488 h / s from the card, which is a total minus 100 h / s from the rig.
But it's still better than competitors because they give out less actual speed on the pool.
All of the above is not a reproach, but for the information of possible owners of similar cards.
I like your miner for stability without rebooting for weeks. Thank you.