What should have happened
Jurors will be instructed along the following lines (Model Jury Instructions, 8.4 - Outside Information):
The only information that you may consider is the evidence that has been put before you in the courtroom. You must disregard completely any information from radio, television, or newspaper accounts, Internet sources, Twitter, Facebook, or any other social media, that you have heard, seen or read about in respect of this case, or about any of the persons or places involved or mentioned in it. Any other information about the case from outside the courtroom, is not evidence.
They will also be instructed about reasonable doubt in relation to expert evidence:
The issue on which these experts... differ is an essential element that the Crown must prove beyond a reasonable doubt. Before you accept the opinion of the Crown’s expert on this issue you must be satisfied beyond a reasonable doubt that s/he is correct. If you are not sure that s/he is correct, then the Crown has failed to prove beyond a reasonable doubt that essential element of the offence charged.
Given that the jurors were waffling, they would have had reasonable doubt and should have acquitted.
Regardless, once a jury verdict is rendered, it is not possible for the trial judge to alter the verdict except where the judge learns that the jury did not render the verdict it intended (R. v. Burke, 2002 SCC 55). Even a judge learning of potential juror bias does not have the power to declare a mistrial after the verdict is rendered: R. v. Halcrow, 2008 ABCA 319.
There are very narrow grounds to appeal a verdict based on a problem with what the jury did
There may be very limited opportunities on appeal:
- if one can show a reasonable apprehension of bias based on evidence that does not include matters intrinsic to the jury room (e.g. R. v. Mehl, 2021 BCCA 264)
- if the verdict was unreasonable in the sense that it was a verdict that no jury, properly instructed and acting judicially, could reasonably return—this is the standard referred to in ohwilleke's answer (in the circumstances you've described, it seemed that there was evidence in the record that the jury could have been convinced by, so your scenario does not seem to meet this high standard for an unreasonable verdict)
Jury-secrecy rules prohibit matters internal to the jury from ever being introduced as evidence
Above all of this are the statutory and common-law jury secrecy rules. The rule in Canada is this (from R. v. Pan; R. v. Sawyer, 2001 SCC 42):
statements made, opinions expressed, arguments advanced and votes cast by members of a jury in the course of their deliberations are inadmissible in any legal proceedings. In particular, jurors may not testify about the effect of anything on their or other jurors’ minds, emotions or ultimate decision. On the other hand, the common law rule does not render inadmissible evidence of facts, statements or events extrinsic to the deliberation process, whether originating from a juror or from a third party, that may have tainted the verdict.
The dividing line between intrinsic matters protected by the jury secrecy rules and extrinsic matters that might be able to be revealed is not always clear, but the evidence you've described seems to be an intrinsic matter:
 Jurors are expected to bring to their task their entire life’s experiences. It is on the basis of what they know about human behaviour, knowledge that they have obviously acquired outside the courtroom, that they are requested to assess credibility and to draw inferences from proven facts. Even though not the object of evidence tendered in the trial, an opinion, a piece of general information, or even some specialized knowledge that a juror may reveal in the course of the deliberations, is not an extrinsic matter. Typically, such information would not be the object of evidence tendered at trial. It would be viewed as either irrelevant, too remote, or as attempting to usurp the functions of the jury. On the other hand, if a juror, or a third party, conveys to the jury information that bears directly on the case at hand that was not admitted at trial, by reason of an oversight or a strategic decision by counsel or, worse yet, by operation of an exclusionary rule of admissibility, then it is truly a matter “extrinsic” to the deliberation process and the fact that it was introduced into that process may be revealed.
 The line between matters of general knowledge and information that bears directly on the case may not always be evident. For example, if a juror shares with his fellow jurors his detailed familiarity with the location where the crime was alleged to have been committed, this may be viewed as an intrinsic matter protected by the secrecy rule. If the same juror, however, went on a visit to the site, took photographs and brought them back to the jury room to support his interpretation of the facts at issue, this may be extrinsic, outside information that falls outside the secrecy rule.