When John Diggle is interrogating Diaz, he carried a loaded sidearm into the room. No seasoned military or government agent would do that. The chances of the prisoner, especially one as dangerous as Diaz, would be too risky of getting the gun and using it.
When Emiko kicks the workout dummy and it breaks, it is clear that the post has been cut by the smooth cut visible through most of it.
When Dinah shows Rene the tattoo on her wrist, it has started to rub off.
At the beginning of the show Emiko is given a hardware token key fob and then uses it to open a secure door. Hardware tokens don't open doors on their own. They display a code that changes at a set frequency (usually 30-60 seconds) and this code can be used, along with a password, to log in to something that requires two-factor authentication.
When Dinah says that SCPD is overloaded with work so analyzing new Green Arrow's blood might get delayed, then Oliver offers her to let old Green Arrow lab analyze the same as they were working together and she gives the blood sample to him. That is not how it works. Even when they are working together, there is no guarantee of Integrity of old Green Arrow, he might be blackmailed or bribed or otherwise pressurized to alter the report, just as any government official doing the analysis can be pressurized. Yet, a government officer is accountable for his deeds and there are procedures to handle that. Old Green Arrow doesn't have any procedure. It just depends on personal integrity of Oliver and Felicity, who would be doing actual analysis, and Dinah will be responsible for using such discretion. If Oliver wanted to help SCPD, he should have handed over his entire lab to SCPD, so that actual government official do the analysis.