I think that this happens because not all people are getting tested.
The cost for a test is high especially if there are so many people to get tested.
So in order to keep the safety on high levels they say that people are positive and they send them in quarantine to be sure that they are not.
not how it works
when someone bothers to actually get themselves tested. and tests positive. they can help by mentioning who they came into contact with. either directly themselves telling their family and friends or by using the public health service to inform the family and friends, where the public health wont reveal the source to the family and friends.
some people dont want grandpa joe knowing they are the cause of grandpa joe maybe being sick next week
but still want to warn him that he might be at risk
..
yea some paranoid idiots will say this 'anonymous' contact by public health of not revealing the source is because there is no source.. but the truth is not the case.
its not about making up false records to force people into quarantine. its about bad processes of mistakes that are usually small examples on small area's which get corrected the process once they realise the mistake
yes some lab in the past have contaminated a couple bottles of the chemical used to do testing which has temporarily made bad results for those limited number of cases in that batch in that lab. but now they improve the process to avoid contaminating the base chemicals used in the tests.
EG instead of barrels of chemicals they use smaller batch bottles. and test each bottle before using it and periodically until they need a new bottle.
they use disposable pipettes and such that are not reused/reintroduced into the process.
yea some swab centres have had bad 'queuing' strategies of linking personal info to certain timeslots/queue numbers. which then mixed up who gets what result because of who didnt turn up or who skipped the queue.
so they learn to change the strategy and validate who is getting swabbed when they actually get swabbed.
there are silly people that turn up and when asked again what is their name to re-validate the person is the person on the list. the person gets angry and paranoid about why this information is being requested again.
so theres a fine line between identifying who is being tested vs not causing the paranoid stupid people to cry like babies shouting government grabbing bigdata.
but the main point is
when an issue is found and resolved they retest. thus get more accurate results.
so yes sometimes you see some numbers change a little to re-count more accurately. and i know the paranoid idiots will use these small 0.x% of cases to drum up some stupid conspiracy that 100% of tests are wrong.. but these paranoid idiots are just to stupid to be corrected even if you try for months.