When using the locate command to find portal ruins, it is sometimes inaccurate

I have experienced this phenomenon also. I suspect that the problem behavior is caused by the user searching for the portal in the Overworld but the /locate command is giving Nether coordinates. I suspect this becomes a problem in this release because Ruined_Portals can generate in either the Overworld or the Nether and the /locate command offers no parameter for specifying the present dimension or a different one. I will investigate further and offer an additional comment once this is confirmed.  Investigation continues below.

I used a portal to go to the Nether and /tp to the coordinates given and there was no portal, ruined or otherwise, at those coordinates at any altitude. I returned to the Overworld and tried the original search, but inverting the sign on each of the coordinates, and teleporting and searching at all altitudes for the new coordinates. No Ruined Portal was found.

The original /locate Ruined_Portal command was issued from coordinates 146. 86. /-383. The returned coordinates were "/-576. /~. /-1104 1019 blocks away." I can attach or make game world files available if requested.

Note: The game world was originally generated by a 1.14 pre-release snapshot and contained previously loaded and modified chunks before being updated to snapshot 20w16a. Is it possible that the locate command is being "fooled" by the Ruined Portal not generating at the coordinates given because the chunk had been previously loaded and modified?

Note: Someone may want to investigate this issue with respect to Bedrock Edition issue MCPE-70691 as possibly being related and link it as such, if it is.

Could be a duplicate of MC-178854. I had the same issue and reported it. I used the locate command to find a ruined portal, but it was not exactly at the the coordinates that the command said. 

I can provide some examples:

seed: -126790419721262898

coord: 144 ~ 992; -336 ~ -560

I tried to dig down at both pos but found no ruined portals.

Updated for 1.16 pre2:

For the coord 144 ~ 992, one is actually found at about 160 54 996.

For the coord -336 ~ -560, couldn't find one at all.

Thank you for your report!
However, we are already tracking this issue, and this report is a Duplicate of MC-178842.

Please use the search function in the future to prevent duplicate reports.

Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – ✍️ Feedback and Suggestions – 📖 Game Wiki