Why is the Coronavirus Test prone to return false positives?

Background information on Polymerase Chain Reaction, which appears to be the standard method of detecting Coronavirus, yields

some clues:

• Because PCR is a highly sensitive technique, any form of contamination of the sample by even trace amounts of DNA can produce misleading results (Bolognia et al, 2008; Smith & Osborn, 2009).

• Another limitation is that the primers used for PCR can anneal non-specifically to sequences that are similar, but not completely identical to target DNA. In addition, incorrect nucleotides can be incorporated into the PCR sequence by the DNA polymerase, albeit at a very low rate.

Sauce:

https://web.archive.org/web/20200630134027/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4102308/

https://web.archive.org/web/20200630134027/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4102308/