Add known issue: Quickly changing the replicationFactor can cause a 412 Precondition failed error (#853)

* Add known issue: Quickly changing the replicationFactor can cause a 412 Precondition failed error

* Capitalization

Author: Simran-B

site/content/arangodb/3.12/release-notes/version-3.12/known-issues-in-3-12.md

@@ -51,3 +51,4 @@ Note that this page does not list all open issues.
 | **Date Added:** 2024-07-03 <br> **Component:** arangod <br> **Deployment Mode:** All <br> **Description:** ArangoDB can crash if run on bare metal and the Linux distribution uses a different glibc version, the `libnss-*` libraries are installed, and the `/etc/nsswitch.conf` configuration file contains settings other than for `files` and `dns` in the `hosts:` line, or the `passwd:` and `group:` lines contain something other than `files`. If you use a fixed version, it can still crash under these circumstances if you enable the `--honor-nsswitch` startup option. <br> **Affected Versions:** 3.11.10 (non-hotfix), 3.12.0 <br> **Fixed in Versions:** 3.11.10-1, 3.12.1 <br> **Reference:** [Incompatibility due to switch to glibc](incompatible-changes-in-3-12.md#incompatibilities-due-to-switch-to-glibc) |
 | **Date Added:** 2025-01-30 <br> **Component:** arangod <br> **Deployment Mode:** Cluster <br> **Description:** If the invariant is violated that ArangoDB's data is not modified while a server is down, manually as well as automatically triggered operations such as moving shards can make a DB-Server the leader (again) even though it may not have the correct data. ArangoDB does currently not protect against certain cases like bringing a DB-Server back without data (by accident or on purpose), which can lead to this empty state getting replicated across the cluster and thus causing data loss. <br> **Affected Versions:** 3.11.x, 3.12.x <br> **Fixed in Versions:** - <br> **Reference:** N/A |
 | **Date Added:** 2025-06-25 <br> **Component:** Web interface <br> **Deployment Mode:** All <br> **Description:** Specifying an `X-Script-Name` HTTP header in requests to the web interface (`/_admin/aardvark`) to add a path prefix is non-functional. The feature was originally added in version 3.0 for basic proxy setups but doesn't adequately handle the requests of certain internal services. <br> **Affected Versions:** 3.11.x, 3.12.x <br> **Fixed in Versions:** - <br> **Reference:** N/A |
+| **Date Added:** 2025-12-09 <br> **Component:** arangod <br> **Deployment Mode:** Cluster <br> **Description:** When rapidly changing the `replicationFactor` of a collection, the server may unexpectedly reply a `Precondition Failed` error with code `412`. <br> **Affected Versions:** 3.12.x <br> **Fixed in Versions:** - <br> **Reference:** [BTS-2279](https://arangodb.atlassian.net/browse/BTS-2279) (internal) |

site/content/arangodb/4.0/release-notes/version-3.12/known-issues-in-3-12.md

@@ -51,3 +51,4 @@ Note that this page does not list all open issues.
 | **Date Added:** 2024-07-03 <br> **Component:** arangod <br> **Deployment Mode:** All <br> **Description:** ArangoDB can crash if run on bare metal and the Linux distribution uses a different glibc version, the `libnss-*` libraries are installed, and the `/etc/nsswitch.conf` configuration file contains settings other than for `files` and `dns` in the `hosts:` line, or the `passwd:` and `group:` lines contain something other than `files`. If you use a fixed version, it can still crash under these circumstances if you enable the `--honor-nsswitch` startup option. <br> **Affected Versions:** 3.11.10 (non-hotfix), 3.12.0 <br> **Fixed in Versions:** 3.11.10-1, 3.12.1 <br> **Reference:** [Incompatibility due to switch to glibc](incompatible-changes-in-3-12.md#incompatibilities-due-to-switch-to-glibc) |
 | **Date Added:** 2025-01-30 <br> **Component:** arangod <br> **Deployment Mode:** Cluster <br> **Description:** If the invariant is violated that ArangoDB's data is not modified while a server is down, manually as well as automatically triggered operations such as moving shards can make a DB-Server the leader (again) even though it may not have the correct data. ArangoDB does currently not protect against certain cases like bringing a DB-Server back without data (by accident or on purpose), which can lead to this empty state getting replicated across the cluster and thus causing data loss. <br> **Affected Versions:** 3.11.x, 3.12.x <br> **Fixed in Versions:** - <br> **Reference:** N/A |
 | **Date Added:** 2025-06-25 <br> **Component:** Web interface <br> **Deployment Mode:** All <br> **Description:** Specifying an `X-Script-Name` HTTP header in requests to the web interface (`/_admin/aardvark`) to add a path prefix is non-functional. The feature was originally added in version 3.0 for basic proxy setups but doesn't adequately handle the requests of certain internal services. <br> **Affected Versions:** 3.11.x, 3.12.x <br> **Fixed in Versions:** - <br> **Reference:** N/A |
+| **Date Added:** 2025-12-09 <br> **Component:** arangod <br> **Deployment Mode:** Cluster <br> **Description:** When rapidly changing the `replicationFactor` of a collection, the server may unexpectedly reply a `Precondition Failed` error with code `412`. <br> **Affected Versions:** 3.12.x <br> **Fixed in Versions:** - <br> **Reference:** [BTS-2279](https://arangodb.atlassian.net/browse/BTS-2279) (internal) |