I tried to find anything specific on the government's site, but it doesn't really tell anything about re-application, other than re-applying in case you contest the decision
If your application is unsuccessful
You can apply again at any time
until 30 June 2021 if you think the decision should have been
different, for example you got pre-settled status but expected to get
settled status.
There’s no charge for this.
You can submit new information or evidence if you want to.
However FreeMovement does cater for the exact scenario you mention:
Mika is from Finland. He moved to the UK in March 2017 and was granted
pre-settled status in March 2019. Mika therefore expects to qualify
for settled status in March 2022.
In March 2020, Mika happens to be in Finland on a visit home and
decides to ride out the coronavirus pandemic there. He eventually
returns to the UK in November 2020. As Mika has been out of the UK for
more than six months, he now can’t qualify for settled status until
November 2025, after completing a continuous residence period of five
years.
As he has been out of the UK for less than two years, he still has
pre-settled status. But that pre-settled status will expire in March
2024, five years after it was granted. Mika can’t extend his existing
pre-settled status beyond March 2024, so would be unable to reach
November 2025. He therefore needs to reapply for pre-settled status
when he returns to the UK in November 2020.
It explicitly says that people can (and should) re-apply in case they have lost their continuous residency during the transition period. While this is not an official government website related to the (pre-)settled status, it was written by solicitors handling immigration issues.
I have found another source - unfortunately also from a solicitor and not from the government - that also suggest you can re-apply:
1.23 Is there a limit on the number of times I can apply for settled status/pre-settled status?
No. You can reapply as many times as you want to before 31 December 2020.
Update: I was just pointed to an official source, which is the EU Settlement Scheme caseworker guidance. On page 25/26 under "Further applications" it says that:
Further applications
(...)
- If the earlier application
resulted in pre-settled status being granted, the further application
must be considered in the normal way
This just approves that re-application is indeed possible. However later it also clarifies what re-application will do:
If you grant pre-settled status where the applicant has pre-settled
status, then it will replace the earlier grant of pre-settled
status. The date of the first grant of pre-settled status will remain
the start date of their pre-settled status. The expiry date of their
pre-settled status will be five years from the date of decision on the
further application for pre-settled status.
For me this means that re-application is both possible and advised, as it will extend the 5 year period.
Also note that you have until 30 June 2021 to apply for pre-settled status - but you need proof that you arrived in the UK before 31 December 2020. Since re-applying is possible and will extend your eligibility the safest thing to do would be to re-apply in December 2020, and then once more around June 2021 to extend the 5 year deadline as much as possible to June 2026