Submitted by peritoflores
Storage collision because of lack of EIP1967 could cause conflicts and override sensible variables
When you implement proxies, logic and implementation share the same storage layout.    In order to avoid storage conflicts  EIP1967 was proposed.(https://eips.ethereum.org/EIPS/eip-1967)   The idea is to set proxy variables at fixed positions (like  impl and admin ).
For example, according to the standard,  the slot for for logic address should be
0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc (obtained as bytes32(uint256(keccak256('eip1967.proxy.implementation')) - 1)  ).
In this case, for example, as you inherits from Ownable the variable _owner is at the first slot and can be overwritten in the implementation.   There is a table at OZ site that explains this scenario more in detail
https://docs.openzeppelin.com/upgrades-plugins/1.x/proxies
section  Unstructured Storaged Proxies
Consider using EIP1967
sofianeOuafir (Joyn) confirmed and commented:
deluca-mike (judge) commented:
