It's like those flat-earth people who did that experiment with the extremely sensitive gyroscope that proved that the earth was rotating and spherical; and were caught on recording saying "well, we clearly cannot accept that" and I think eventually simply deliberately ignored and suppressed it from their minds.
Do not ever underestimate certain human's capacity for self-delusion.
The bigger problem though is that this UBI cult is very authoritarian and tyrannical at its core, consistently increasing the insistence that they must take and use ever increasing amounts of other people's money to prove that UBI works, coincidentally making the researchers and the common NGO types scam artist operatives huge amounts of money in the process.
UBI is simply a con job, a fraud, a lie, theft, and even slavery ... theft of resources and services against their will and under threat of violence and harm in order to support the lives and livelihoods of others.
You want UBI? Great, sign up to have your income taxed to pay for it.